. In crowded places like airports and railway stations you take care of your luggage. A.

问题补充：

. In crowded places like airports and railway stations, you take care of your luggage.

A. can

B. may

C. must

D. will

答案：

A. can

B. may

(答案→)C. must

D. will

解析：must在此表示“必须”。句意为：在像机场和火车站这样的比较拥挤的地方，你必须要看好自己的行李。