Hi @soumita and @gmat6087,

This is a good parallelism question, one that exemplifies the importance of identifying the intended parallel list.

What is the original sentence telling us?

Its talking about the belief of scientists regarding what all global warming could lead to. Global warming could lead to a few things. Here they are:
1. Increase in Precipitation
2. Increase in Evaporation
3. Decline in Soil Moisture
4. Conversion of Desert lands into current rangelands.

These four things appear to be at the same level. However, focus on the last element "a resulting increasing of desert lands into current rangelands". The use of "resulting" here implies that this effect is due to the preceding three impacts # 1, 2, and 3. Now how do we express result of a clause. You may use a verb-ing modifier, or you may use the construction as is used in choice B in this question.

Why C is incorrect - it is not parallel. "an increase in ..." is not parallel to "declining soil moisture".

Why E is incorrect - This is a smartly worded choice. It appears to be parallel - all are verb-ing + noun forms. But look at the construction of these elements and notice that this construction does not communicate the intended meaning.

Increasing precipitation is not the same as increase in precipitation.

Increase in precipitation - Per the context of the sentence, this phrase suggests that global warming will eventually lead to a rise in precipitation. There will be gradual rise in the level of precipitation.

Increasing precipitation -Here "increasing" is an adjective that modifies "precipitation". It seems to denote the continuity in the action. And continuity in action is not the intended meaning of the sentence.

Lets take a simple example:
The rising crime in the city has led to increased police vigilance. - This sentence implies that the crime is still rising. There is a continuous increase in crime.

The rise in crime in the city has led to increased police vigilance. - This sentence implies that rise in crime has happened. It's now at an increased level.

I hope this helps clarify your confusion. I suggest you review a few correct official sentences. Take some in which correct answer has verb-ing form as in choice E. Notice the sense that those elements communicate. Take some in which the correct form is as in choice B. Notice the sense communicated in those. This will help cement the difference in your mind. And remember another key point:

Parallelism is not just about maintaining similarity across all elements. It is about making sure that the elements are logically parallel and that the elements communicate the intended meaning. For more on logic vs grammar on parallelism click here .

Regards,

Payal