Other experiments have shown 【61】 the brain needs time to "digest" 【62】has been learned. The time necessary 【63】 this is 5 to 10 minutes. After a break of this period of time the memory will have 【64】 what has just been learnt, and more will be remembered. During this break, 【65】 is important to exercise the right side of the brain, 【66】 the left side is used during a learning period. 【67】 you should relax in some way. 【68】 music, breathing in fresh air, and 【69】 at a picture, are all ways of using 【70】 side of the brain.
(61)

A. that
B. what
C. which
D. it