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?