A:最小光圈
B:较大光圈
C:高倍物镜
D:最小焦距
己知集合A={1,2,3,4},B={xx2﹣2x﹣3≤0},则A∩B=( )
— It was ___________ who helped us out of danger.— What brave and helpful children! We should learn from them.