题目内容
19. By the time he was fourteen,Einstein advanced mathematics all by himself.(learn)
爱因斯坦到十四岁时就自学完了高等数学。
19. had learned考查by the time引导的时间状语从句 by the time意为"到. 时为止",主句一般要用完成时态。从句为一般过去时,主句要用过去完成时。
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19. By the time he was fourteen,Einstein advanced mathematics all by himself.(learn)
爱因斯坦到十四岁时就自学完了高等数学。
19. had learned考查by the time引导的时间状语从句 by the time意为"到. 时为止",主句一般要用完成时态。从句为一般过去时,主句要用过去完成时。