Look, so many passengers _________ with their smart phones on the underground.
A:played
B:will play
C:are playing
D:have played
某导体两端的电压为12伏,通过它的电流为0.6安,10秒内通过该导体横截面的电荷量为____ 库,其电阻为____ 欧.当它两端的电压为6伏时,通过它的电流为____ 安.
寒冷的冬天,法国梧桐纷纷落叶,松树却依然郁郁葱葱,这表明了( )