题干
Her mother often forgets the door but this morning she remembered it.
A：to close; to close
B：closing; closing
C：to close; closing
答案(点此获取答案解析）
C
Her mother often forgets the door but this morning she remembered it.
A：to close; to close
B：closing; closing
C：to close; closing
，则a与b夹角为（ ）
