Drivers must _________ seat belts while their cars are running on the road.
A:dress
B:in
C:wear
D:put on
小华在“探究小灯泡的亮度与哪些因素有关”的实验中,所用电源电压恒为3V,小灯泡上标有“2.5V”字样
Summer is hot.____
下列哪种光学仪器成像原理与人眼球成像原理一样?____(选填序号)
①照相机 ②放大镜 ③投影仪 ④潜望镜.