If you want to see a doctor fix the date with him ahead of time. This is a common in th

问题补充：

If you want to see a doctor, fix the date with him ahead of time. This is a common in the USA.

A. habitB. lawC. ruleD. custom

答案：

解析：本题是典型的词语辨析题，habit通常为“生活习惯”，law为“法律”，rule为“条文规定”，custom为“习惯”，所以D项符合题意。