问题补充：
We must keep our room clean, for dirt and disease go, you know.
A. hand in hand
B. step by step
C. from time ti time
D. one zfter another
答案：
(答案→)A. hand in hand
B. step by step
C. from time ti time
D. one zfter another
解析：句意：我们必须保持室内卫生，你知道脏乱与疾病是分不开的。hand in hand---happenning together and closely connected密切相关的，同时发生的。本句还可说成：Dirt goes hand in hand with disease.
