题目

. .---Who ________ it be that is knocking at the door? ---It________ be Mother, but I’m not sure.   A. can; must          B. can; may           C. must; can   D. may; must 答案：B10．45米的$\frac{3}{5}$是27米．15千克的$\frac{4}{5}$是12千克．