By the time a children turn two years old, their brains have grown to about percent of their adult size.

ANSWER:

By the time a children turn two years old, their brains have grown to about '80 percent' of their 'adult size'.

EXPLANATION:

There is variation of growth while comparing in growth of body and the growth of brain. Basically, the process of brain growth is much faster. By the age of five, a child’s brain grows is complete 100 percent. There had been a survey about what time must be the accurate time for the proper development of brain as well as body is up to 3 years old.

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