在下降后期大部分床层已经紧密，分层作用几乎完全停止，所以这段时间应尽量延长
参考答案：错
—I wonder if you could go with me to the supermarket.
—Sorry. I _______ my experiment report all the morning and haven’t finished yet.
A．write
B．was writing
C．have written
D．have been writing
下列不属于配子基因型的是（）
A.Ab
B.ab
C.Aa
D.AB
