B. She silently comforts her friend by squeezing his hand.
Answer:
I would say the effects of high-fat and low-fat diets.
Explanation:
For [A] a report on how to reduce air pollution would be expository or persuasive.
For [B] a mystery story would be entertaining and engaging.
For [C] why Great Britain was the birthplace of the industrial revolution would be a persuasive exposition, factually based.
For [D] you would write and exposition comparison to describe the benefits and detriments of the two types of diets, thus a "compare-and-contrast" essay.
Cheers.
