（）受损就意味着指甲停止生长或畸形生长。
A.甲根
B.甲弧
C.甲床
D.甲母
参考答案：D
同一个总体，时期指标值的大小与时期长短成正比，时点指标值的大小与时点间隔成反比。（）
William Sidney Porter, known as O. Henry, is most famous for ______.
A. his poems B. his playsC. his short stories D. his novels
