It when I my homework last night. ( )
A:raining, did
B:rained, was doing
C:was raining, do
D:rains, was doing
如图所示,小聪同学在“探究凸透镜成像规律”实验时,烛焰在光屏上成了一个清晰的像,下列说法正确的是( )
读成渝经济区城际铁路规划示意图,完成下面小题。
如图所示的实验现象所揭示的原理或规律与所对应的应用不正确的是( )