A:①②④
B:②③④
C:①②③
D:①③④
——Do you think the rain will stop tomorrow?——_______. It has rained for ten days. It's too wet everywhere.
如图是光学显微镜的一组镜头,①②为目镜标有5×字样和15×字样,③④为物镜标有10×和40×字样。则用此组镜头要达到最大放大倍数时所选用的镜头组合是