The children are swimming . . . . . . . . the pool. A. behind B. between C. at D. in

The correct answer is D. The children are swimming in the pool.

The other options are incorrect because they do not accurately describe the location of the children.

• Option A, behind, is incorrect because the children are not swimming behind the pool. They are swimming in the pool.
• Option B, between, is incorrect because the children are not swimming between the pool and something else. They are swimming in the pool.
• Option C, at, is incorrect because the children are not swimming at the pool. They are swimming in the pool.

The word “in” is the most accurate word to describe the location of the children because they are inside the pool.