A:二氧化碳
B:氧气
C:氮气
D:稀有气体
People work together to keep the Earth health.
____改为____
——What do you think of the woman singer?
—— Her voice sounds _____. I like her songs.
在“测量小灯泡电阻”的实验中,电源电压为3V,小灯泡的额定电压为2.5V.