Critical Reasoning

Twenty years ago, Balzania put in place regulations requiring operators of surface mines to pay for the reclamation of mined-out land. Since then, reclamation technology has not improved. Yet, the average reclamation cost for a surface coal mine being reclaimed today is only four dollars per ton of coal that the mine produced, less than half what it cost to reclaim surface mines in the years immediately after the regulations took effect.

Which of the following, if true, most helps to account for the drop in reclamation costs described?

A. Even after Balzania began requiring surface mine operators to pay reclamation costs, coal mines in Balzania continued to be less expensive to operate than coal mines in almost any other country.
B. In the twenty years since the regulations took effect, the use of coal as a fuel has declined from the level it was at in the previous twenty years.
C. Mine operators have generally ceased surface mining in the mountainous areas of Balzania because reclamation costs per ton of coal produced are particularly high for mines in such areas.
D. Even after Balzania began requiring surface mine operators to pay reclamation costs, surface mines continued to produce coal at a lower total cost than underground mines.
E. As compared to twenty years ago, a greater percentage of the coal mined in Balzania today comes from surface mines.

Key to getting this question right are clearly understanding what the prompt says and noticing whether what each answer choice says is really logically related to what the prompt says and what the question is asking.

One interesting aspect of this question is that two of the answer choices could be used for making up stories that would explain the cost decrease. Below I explain why doing that will not get you to the right answer.

A. Even after Balzania began requiring surface mine operators to pay reclamation costs, coal mines in Balzania continued to be less expensive to operate than coal mines in almost any other country.

The prompt and question are not about expense relative to expense in other countries.

B. In the twenty years since the regulations took effect, the use of coal as a fuel has declined from the level it was at in the previous twenty years.

This answer is a trap in a way, because you could make up some story in your mind that would connect what this says to the reduction in costs. Making up stories in your mind is a great way to get the wrong answer to a critical reasoning question. Anything that is not directly stated must be clearly logically indicated by what is said in the prompt and answer choice and not a roundabout story that you might come up with. As a matter of fact, you could also base on what this answer choice says a story that would explain an increase in cost of reclamation.

C. Mine operators have generally ceased surface mining in the mountainous areas of Balzania because reclamation costs per ton of coal produced are particularly high for mines in such areas.

If technology has not improved, there must be some other change that accounts for the reduction in costs. This answer choice describes such a change. The mine operators have reduced the amount of mining they do in certain types of areas.

D. Even after Balzania began requiring surface mine operators to pay reclamation costs, surface mines continued to produce coal at a lower total cost than underground mines.

The question is about a change in reclamation costs, not about the relative costs of different types of mines.

E. As compared to twenty years ago, a greater percentage of the coal mined in Balzania today comes from surface mines.

This is another answer choice that you could use to make up a story that would explain why the costs have decreased, but it does not own its own actually include anything that indicates exactly why they have.

The correct answer is C.

Twenty years ago, Balzania put in place regulations requiring operators of surface mines to pay for the reclamation of mined-out land. Since then, reclamation technology has not improved. Yet, the average reclamation cost for a surface coal mine being reclaimed today is only four dollars per ton of coal that the mine produced, less than half what it cost to reclaim surface mines in the years immediately after the regulations took effect.

Which of the following, if true, most helps to account for the drop in reclamation costs described?

When a passage asks us to account for an APPARENT CONTRADICTION:

1. Identify the TWO FACTS that seem to contradict each other.
2. Look for an answer choice that explains HOW BOTH FACTS CAN BE TRUE at the same time.

In the passage above:

Fact 1: Reclamation TECHNOLOGY has not improved.
Fact 2: The AVERAGE COST of reclamation has decreased significantly.

Question: How can both facts can be true at the same time?
Answer: There must be a REASON that the AVERAGE COST of reclamation has decreased significantly.

A. Even after Balzania began requiring surface mine operators to pay reclamation costs, coal mines in Balzania continued to be less expensive to operate than coal mines in almost any other country. Outside the scope. The argument is not about the cost of OPERATING the coal mines but about the cost of RECLAIMING the coal mines.

B. In the twenty years since the regulations took effect, the use of coal as a fuel has declined from the level it was at in the previous twenty years. Outside the scope. The argument is not about the USE OF COAL but about the cost of RECLAIMING the mines. While the USE OF COAL might affect PROFITS, it does not affect the ratio of reclamation COSTS to production COSTS.

C. Mine operators have generally ceased surface mining in the mountainous areas of Balzania because reclamation costs per ton of coal produced are particularly high for mines in such areas. Bingo! This answer choice explains why the AVERAGE cost of reclamation has DECREASED: mine operators are no longer operating in areas where the cost of reclaiming a mine is HIGH, thus lowering the AVERAGE cost of reclamation.

D. Even after Balzania began requiring surface mine operators to pay reclamation costs, surface mines continued to produce coal at a lower total cost than underground mines. Does not explain why the ratio of RECLAMATION COSTS to PRODUCTION COSTS has decreased.

E. As compared to twenty years ago, a greater percentage of the coal mined in Balzania today comes from surface mines. Outside the scope. Does not explain why the average cost of RECLAIMING a mine has decreased.

The correct answer is C.

sukhman wrote:Twenty years ago, Balzania put in place regulations requiring operators of surface mines to pay for the reclamation of mined-out land. Since then, reclamation technology has not improved. Yet, the average reclamation cost for a surface coal mine being reclaimed today is only four dollars per ton of coal that the mine produced, less than half what it cost to reclaim surface mines in the years immediately after the regulations took effect.

Which of the following, if true, most helps to account for the drop in reclamation costs described?

A. Even after Balzania began requiring surface mine operators to pay reclamation costs, coal mines in Balzania continued to be less expensive to operate than coal mines in almost any other country.
B. In the twenty years since the regulations took effect, the use of coal as a fuel has declined from the level it was at in the previous twenty years.
C. Mine operators have generally ceased surface mining in the mountainous areas of Balzania because reclamation costs per ton of coal produced are particularly high for mines in such areas.
D. Even after Balzania began requiring surface mine operators to pay reclamation costs, surface mines continued to produce coal at a lower total cost than underground mines.
E. As compared to twenty years ago, a greater percentage of the coal mined in Balzania today comes from surface mines.

Nice cr!
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This is an old 700+ GMAT Prep question(not in current), I have posted the image...
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