2. 表示“當(dāng)…時候”的 while, when, as 的用法區(qū)別是：while從句中的謂語動詞必須是延續(xù)性動詞；表示帶有規(guī)律性的“每當(dāng)”或當(dāng)主、從句謂語動詞的動作發(fā)生有先后時，只能用 when；當(dāng)表示“一邊…一邊…”或“隨著”時，只能用 as。另外，用于此義的 as 所引導(dǎo)的時間狀語從句謂語只能是動作動詞，不能是狀態(tài)動詞。如下面一道高考題的答案是 B 而不能是A：
“I’m going to the post office.” “_____ you’re there, can you get me some stamps?”
A. As B. While C. Because D. If
3. until 在肯定句中通常只連用延續(xù)性動詞，表示相應(yīng)動作結(jié)束的時間；在否定句中通常連用非延續(xù)性動詞，表示相應(yīng)動作開始的時間，意為“直到…才”。如：
He waited until she was about to leave. 他等著一直到她準(zhǔn)備離開。
I did not begin to work till he had gone. 他走了后我才開始工作。
4. 表示“一…就”除用 as soon as 外，還可用 the minute, the second, the instant, immediately, directly, instantly, no sooner…than, hardly…when 等。如：
I came immediately you called. 你一來電話我就來了。
Hardly had she arrived when it began to snow. 她剛到就下起雪來了。
The moment I have finished I'll give you a call. 我一干完就給你打電話。
5. every time, each time, (the) next time, (the) last time, by the time, the first time, any time 等以 time 結(jié)尾的詞語也可用作連詞，引導(dǎo)時間狀語從句。如：
Next time you come in, please close the door. 下次你進來，請關(guān)門。
He didn’t tell me anything the last time I saw him. 上次我見到他時他什么也沒告訴我。
By the time I got home, she had already gone to bed. 我到家時她已睡覺了。
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