有关胎盘描述哪项不正确
A.妊娠12周基本形成B.直径为18-20cm C.胎盘重600-1000gD.由18-20个胎盘小叶组成E.母面暗红而粗糙
参考答案:C
—Mike’s parents have bought a 2-floor house with a swimming pool.
— Oh, it________ be very expensive.
A.must
B.can
C.need
D.should
有源逆变指的是把()能量转变成()能量后送给()装置。