黑素细胞占基底层细胞的比例约为（）。
A.30％
B.40％
C.50％
D.90％
E.10％
参考答案：E
—How do you study for your test?
—I study by _____ to the radio. [ ]
A. listen
B. listening
C. to listen
D. listened
_________your success. [ ]
A. Congratulate
B. Congratulate on
C. Congratulates
D. Congratulations on
