He had to put his shoes lightly, _____ he? [ ]
A. didn't
B. did
C. had
D. hadn't
答案:A
一块长600厘米、宽300厘米的塑料膜,面积是______平方米.
如图显示在一池塘内四种绿藻(W、X、Y、Z)在不同水深的分布状况.哪一种绿藻最能适应弱光的环境?( )
A.W
B.X
C.Y
D.Z