mary with her parents often ( )a walk in the park

題目：

mary with her parents often ( )a walk in the park
mary with her parents often ( )a walk in the park after supper.a,has
b,have c,is having d,having

解答：

A
因爲主語是Mary,單三形式
B 是複數
C 進行時不可和often 連用
D 單獨一個非謂語動詞不可以做謂語