对静电现象的认识,下列说法中正确的是( )
A:同种电荷相互吸引,异种电荷相互排斥
B:自然界只存在正、负两种电荷
C:从静电现象认识到原子核是可分的
D:摩擦起电创造了电荷
下列有关哺乳动物骨、肌肉和关节的叙述不正确的是( )
例:A:Jenny often walks to school.
B:Jenny walked to school yesterday.
C:Jenny is going to walk to school tomorrow.