C:1/16
A:1/4
B:1/8
D:1/9
保卫细胞区别于叶表皮细胞的结构特点是( )
The kindhearted man,who thinks ________his duty to help poor people,is popular with many people who know him.
用“分子的观点”解释下列现象,不正确的是( )