在现代农业和林业的生产中,利用植物的根尖和茎尖、叶片,甚至一个植物细胞来繁殖新个体.这是利用植物细胞的
( )特性.
A.向肥性
B.变异性
C.向光性
D.全能性
答案:D
If he _________ more time practicing speaking English before, he ____ able to speak it much better now.
A.spent; will be
B.had spent; would have been
C.spent; would have been
D.had spent; would be
硬盘是硬盘驱动器、硬质合金做的硬盘片、硬盘控制器的总称。( )