题干
—How are you doing, Daisy?
— , thank you.
A：I'm OK
B：I'm a teacher
C：I'd love to
D：I'm coming
答案(点此获取答案解析）
A
—How are you doing, Daisy?
— , thank you.
A：I'm OK
B：I'm a teacher
C：I'd love to
D：I'm coming
cause he used to live in the apartment.
的中点，试判断四边形OACB形状，并说明理由．