凸透镜在成缩小像时,对光有会聚作用,在成放大像时,对光有发散作用. (判断对错)
下列说法正确的是( )
“橘生淮南则为橘,橘生淮北则为枳;叶徒相似,其实味不同。”这句话反映了农业生产的( )
When Tim ________ why he was late for school, he just kept silent.