—Betty, come and have a look.

—Oh, ______ nice Mp4 player! I like it. [ ]

A. how

B. what

C. what a

D. how a

设g(x)可导，且x→0时，g(x)是x的高阶无穷小，则当x→0时，必有
(A) g′(x)是无穷小量．
(B)

是x²的高阶无穷小．
(C)

是无穷大量．
(D) 若G′(x)=g(x)，则G(x)是x高阶无穷小．