What is the author's attitude toward DNA testing?
A. Negative.
B. Positive.
C. Suspicious.
D. Indifferent.
Which of the following statements about graphene is true?
A. It is visible to the human eye.
B. It is possibly the thinnest material in the world.
C. It Can Be used to make paper.
D. Finding it Demands time and money.
A. discoverB. repairC. fixD. maintain
A. discover
B. repair
C. fix
D. maintain
请在第_____处填上正确答案。
A. borrowed
B. delivered
C. designed
D. gathered