A:氮气的电子式:
B:硫原子的结构示意图:
C:溴化钠的电子式:
D:水分子的结构式:
13-2和3+2的关系是( )
It was in his ____ (forty)that Liu Cixin completed his famous novel Three bodies.
The old memories which are always thought of b____ us to the happy days.
如图为生产者、消费者和分解者的关系示意图,下列说法正确的是( )