The doctor told me to take the medicine .
A. every fourth hours
B. each fourth hour
C. each four hours
D. every four hours
网友回答
A. every fourth hours
B. each fourth hour
C. each four hours
(答案→)D. every four hours
解析：句意：医生告诉我要每四个小时吃一次药。表示每几个小时，every +基数词+复数名词；或every+序数词+单数名词。故选D。