Choose the topic sentence that best fits the paragraph below.
Scientists studied people who learned the new skill of
juggling. The juggling practice did help the brain grow larger, but it shrank back to normal once the person finished practicing the new skill. It seems that the brain both grows and shrinks with the learning of a new skill.
A. Juggling is a difficult skill to learn for people of all ages.

B. Learning too many skills may cause the brain to grow to a larger size than what is considered healthy by doctors.
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C. There are many ways to grow the brain, but only some of these methods cause permanent growth.

D. Studies show that even though the brain grows during a learning
process, it shrinks back to normal once the process is over.