核心问题
按照语法规则，在含有 since 从句的主句中要使用完成体形式。如果主句中有情态助动词时该怎么办呢？
词典解答
含有 since 从句的主句中含有情态助动词时,可以使用非完成体形式:
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(Ever) Since my teeth were pulled out I can't eat anything solid. 自从我拔了牙以后就不能吃固体食物。
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I have to use crutches (ever) since I had a car accident. 自从我出了车祸后,我就得用拐杖了。
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They won't smoke (ever) since they saw a film on lung cancer. 他们看了一部有关肺癌的影片后，就坚决不再吸烟了。
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He can't get about much since he had that accident. 他在那次事故后就不能多走动了。sincerely