问题补充：
单选题Wemustkeepourroomclean,fordirtanddiseasego______,youknow.A.hand in handB.step by stepC.from time ti timeD.one zfter another
答案：
A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.
