A:NO
B:BO
C:CO
D:DO
____ He's my brother.
____ Who's that boy?
____ Yes, she is.
____ Is she your mother?
____ No, he isn't. He's my teacher.
____ Is he your father?
“封建亲戚,以藩屏周。”说明西周时期实行分封制的主要目的是( )
①卵母细胞的采集和培养 ②精子的采集和获能 ③受精 ④胚胎的早期培养