A highly controversial explanation proposed by string theorists is that ______.
A. magnetic fields affect gravity subtly
B. G is larger near the Earth's poles
C. G has a number of hidden dimensions
D. discrepancies emerge between measures of G
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How many months old does child play with sounds not only for enjoyment？
A. three months
B. two months
C. five months
D. six months
From the passage we can learn that ______.
A. the teenage brain is a kind of work in progress
B. the new brain scans support the conventional thought
C. the brain's frontal cortex becomes bigger during the teenager years
D. at the age of 11 or 12 teenagers are unable to find out people's true feelings
Which of the following statements is TRUE？
A. Credit cards have more advantages than travelers' checks.
B. Dollar bills are as convenient as credit cards.
C. One-cent coins have been withdrawn from circulation.
D. You can increase your credit limit as you like.
The problem of deciding at what point a baby's imitations can be considered as speech ______.
A. it remains unclear so far and remains to be further observed and made clear
B. is important because words have different meanings for different people
C. is one that can never be properly understood because the meaning of words changes with age
D. is one that should be completely ignored because children's use of words in often meaningless
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