____(This/What) is a ____(girl/boy).
What's ____(his/her) name?
____ (His/Her) name is Li Hong.
探究凸透镜成像规律时,小明在凸透镜前放一燃着的蜡烛,移动光屏并在光屏上找到清晰的像.然后将蜡烛远离透镜,调节光屏再次找到一个清晰的像,比较两像( )