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通常两者都可使用，但动词不定式常常用于特定的动作，动名词则用于一般情况（参见下面E）：
It’s sometimes as cheap to buy a new one as（it is）（to）repair the old one．
Buying a new one is sometimes as cheap as repairing the old one．
有时买一个新的跟修理旧的一样便宜。
He found that lying on the beach was just as boring as sitting in his office．
He found lying on the beach just as boring as sitting etc．
他发现躺在沙滩上和坐在办公室里一样没趣／烦人。
He thinks it（is）safer to drive himself than（to）let me drive．
He thinks that driving himself is safer than letting me drive．
他认为自己开车要比让我开车更安全些。
It will soon be more difficult to get a visa than it is now．
Getting a visa will soon be more difficult than it is now．
不久之后，签证会比现在更难拿到。
D 上面C所述的这种比较句式中，如as／than前面用的是动词原形，则常在as／than后面用动词原形而不用动名词。与此相同，如as／than前面用的是动名词，则在其后面一般也使用动名词，而不用动词原形，见前面的例子。位于as／than之前的限定动词＋this／that／which后面多跟动名词，虽也可跟动词不定式：
I’ll deliver it by hand；this will be cheaper than posting it．
我自己送过去，这样比邮寄要便宜。
He cleaned his shoes，which was better than doing nothing．
他把自己的鞋擦了，这总比无事可做好。
E 动词原形与would rather／sooner连用（参见第297与第298节）：
Most people would rather work than starve．
多数人宁可工作也不愿挨饿。
I would resign rather than accept him as a partner．
我宁可辞职也不愿接受他为合伙人。
时间从句
A 时间从句由下列表示时间的连词来引导：
after immediately till／until
as nosooner…than when
as soon as since whenever
before the sooner while
hardly…when
时间从句也可由 the minute，the moment来引导。
用 when，as，while的例句，参见第331节至第333节。
用 before的例句，参见第195节B。
B 请留意，时间从句中不用将来时态或条件时态。
1 如将下列将来时态放入时间从句中，须将它变为一般时态。
一般将来时：
You’ll be back soon．I’ll stay till then．
你会很快回来，我一直等到那时。相当于：
I’ll stay till you get back．
我一直等到你回来。
be going to形式：
The parachutist is going to jump．Soon after he jumps his parachute will open．
跳伞运动员要往下跳。他刚跳之后不久，降落伞就会打开。
现在进行时用做一般将来时和将来进行时：
He’s arriving／He’ll be arriving at six．
他将在 6点到。
但是：
When he arrives he’ll tell us all about the match．
等他到了，他会好好给我们讲讲那场比赛。
Before he arrives I’ll give the children their tea．
在他来到之前，我会给孩子们吃茶点的。
如进行时态表示某一行动在继续，则其完全可以用在表示时间的从句中：
Peter and John will be playing／are playing／are going to play tennis tonight．While they are playing（during this time）we’ll go to the beach．
今晚彼得和约翰要去打网球。他们打球时，我们将去海滨。
2 在时间从句中，将来完成时变为现在完成时，将来完成进行时变为现在完成进行时：
I’ll have finished in the bathroom in a few minutes．
我一会儿就用完浴室了。
The moment／As soon as I have finished I’ll give you a call |
