A:N2H4
B:N2O4
C:NH3
D:NO2
建造高大的铁塔,关键要做到稳定不倒。( )
After school, we usually play ______ basketball for half ______ hour on the playground.
300个同学乘4辆汽车去效游。前3辆车各坐76个同学,第4辆车要坐多少个同学?