When you're asked to evaluate a conclusion in Critical Reasoning, you're really being asked - could this conclusion be valid? These questions are actually very closely related to "find the assumption" questions. Instead of just directly stating what the assumption or logical flaw is, though, these problems will phrase the flaw as a question.

So, ask yourself - what information are we missing? In this case, the conclusion isn't directly stated. We're asked to determine the impact on company profits. This implies that if there's a beneficial impact, Tanco will switch to potassium chloride (KCl), and if there isn't, the company won't. So what information do we need to come to a conclusion about profits?

Remember that profit = revenue - cost. If you ever see a CR question that mentions profit, ask yourself what you know about revenue and cost. In this argument, we're given information about the cost of disposal of salt water. But is that the only cost we have to consider? What about materials costs, production costs, and sales costs? Will those all be the same? And do we have any information about revenue? We'd need to know whether Tanco will be able to generate comparable revenue using KCl. We're told that KCl by-product can be turned into fertilizer, leading to low volume. But does low volume mean low cost? Maybe, but not necessarily.

You'll notice that each answer choice is posed as a question. When you're analyzing each of the answer choices, ask yourself - what would a "yes" answer mean to profits? What would a "no" answer mean? (Or if it's not a yes/no question, consider the extremes).

(A) What difference, if any, is there between the cost of the common salt needed to preserve a given quantity of animal hides and the cost of the potassium chloride needed to preserve the same quantity of hides?
This speaks to materials costs. "No difference" would support the switch to KCl; "much higher cost" would argue against the switch.

(B) To what extent is the equipment involved in preserving animal hides using common salt suitable for preserving animal hides using potassium chloride?
This speaks to production costs. "Very suitable" would support the switch to KCl; "not suitable" would argue against the switch, because they'd have to spend more on new equipment.

(C) What environmental regulations, if any, constrain the disposal of the waste generated in reprocessing the by-product of potassium chloride?
This speaks to costs of disposal. "No regulations" would imply that costs of KCl are low; "costly regulations" would mean that KCl isn't any less costly than salt.

(D) How closely does leather that results when common salt is used to preserve hides resemble that which results when potassium chloride is used?
This speaks to revenue. "Very close resemblance" would suggest that this leather would sell just as well, and revenue would be similar; "not very close resemblance" might mean that this leather won't sell as well.

(E) Are the chemical properties that make potassium chloride an effective means for preserving animal hides the same as those that make common salt an effective means for doing so?
This... doesn't actually speak to any revenue or cost issue. "Are the chemical properties the same" seems to speak to our question "will we have a similar product?" But in fact, they tell us that KCl is "an effective means for preserving." If it's an effective result, do you care how it got there?

To ask the question another way - take Splenda and Sweet-n-Low. They both sweeten coffee without adding calories. Are the chemical properties the same? Probably not. Do you care? Nope. The effect is all that matters.

Hope this helps!