问题补充:
We must keep our room clean. Dirt and disease go you know.
A. from time to time
B. hand in hand
C. step by step
D. one after another
答案:
A. from time to time
(答案→)B. hand in hand
C. step by step
D. one after another
解析:本题是关键是理解句子的含义。“我们必须保持屋子干净,要知道灰尘总是伴随疾病。(灰尘和疾病总是手拉手。)”故B项符合题意。