_____youunderstandthisrule，you‘llhavenodifficultyindealingwithsuchproblems.
A、WhileD
once 意思是 “一旦 ”。while “ 当⋯⋯ 时候 ” ;though“虽然”;unless “除非 ” 。“一旦 你明白了这个规则，处理类似的问题就不困难了。 ”显然， d 符合句子意思的表达需要。
William has cut his smoking_____to five cigarettes a day.
I ‘ve been telling you_____not to do that ，but you neve listened to me.That ’s why you gotinto trouble.
Children who are over-protected by their parents may become_____.
It‘s_____mypowertomakefinaldecisiononthematter.
Itseemsasifthesun_____roundtheearthsinceitrisesintheeastandsetsinthewest.
