Little Tom was frozen with fear when the accident happened, so he just gave some ________ answers when asked about what he witnessed.
A:concrete
B:abundant
C:apparent
D:vague
以氢原子为例,如图的四个图中能正确示意氢原子结构的是( )
如图,已知l1∥l2,∠A=40°,∠1=60°,∠2=____ .
我会填
明:共____画,是____结构。
鲜:共____笔,第四画是____。