使用显微镜时，若光线过强，可选用 [ ]
A．平面镜、小光圈
B．凹面镜、大光圈
C．平面镜、大光圈
D．凹面镜、小光圈
A
圆锥的高不变，底面半径扩大3倍，体积就扩大3倍。[ ]
—Excuse me, is there a post office near here?
— _______ I can’t hear clearly.
A．What’s the matter with you?
B．I beg your pardon?
C．What’s up?
D．What’s wrong?
