求教一道英语选择题,最好解释下.

问题描述:

求教一道英语选择题,最好解释下.
20.Though
he was born and brought up in America,
he can speak ________ Chinese.A.smooth B.fluent C.fluid D.flowing

B fluent 流利的.虽然他在美国出生长大,他能说流利的中文.