____ we have finished the course, we shall take a new one.
A. Now that B. Since that C. Since now D. By now(全国研考)
我知道答案为A（Now that）。但now that引导的是什么从句呢？
R.Quirk等人指出now（that)无论指现在或指过去，都同时表示时间和原因。因此，有时候，我们简直无法断定now（that)引导的从句是时间状语从句，还是原因状语从句。例如：
We are happy now that everybody is present. (CGEL)
(a) 现在大家都到齐了,我们很高兴。
(b) 由于大家都到齐了,我们很高兴。
但是, now (that) 引导的从句并不总是在相等的程度上表示时间和原因。有时候, 时间意味强一些, 有时候, 原因意味强一些。
A. now (that) 表示时间：
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Now (that) I've heard the music I understand why you like it. (LDCE) 现在我听到了这首乐曲,我才明白你为什么喜欢它。
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Now that she's found him, she'll never let him go... 现在她找到了他，绝不会让他走了……
B. now that 表示原因：
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Now that a tunnel has been built through the mountains, the Pass is less dangerous. (NCE, Book 3, L.8) 由于修建了穿山隧道，隘口已经不那么危险了。
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Now (that) you are well again you can travel. (ALD) 你既然已恢复健康,可以去旅游了。
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I am not earning my own income now that my husband is President. (Hillary, Living History) 因为我丈夫当总统，我现在的收入不算自己挣的。（希拉里，《亲历历史》）请做下面的英语试题：
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____ we have finished the course, we shall start doing more revision work.
A. For now B. Now that C. Ever since D. By now(全国四级,90.1-62)
- ____ that my head had cleared, my brain was also beginning to work much better.
A. For B. Now C. Since D. Despite(全国四级,97.6-57)