Working Memory Is Important When People Are Trying to Solve

Working memory is important when people are trying to solve an algebra "word problem" because

A) you need to keep the important parts of the problem in your mind while working on the problem.
B) these problems usually involve objects that have different shapes and sizes, so it's naturally a difficult task.
C) these problems do not use the phonological loop, so it's especially difficult to discover the solution.
D) people often miss the obvious solution, and they therefore have to try again.