if从句中的动词用一般过去时,主句中的动词用条件时态:
If I had a map I would lend it to you.
我要有地图就借给你。(但我没有地图。句子的含义是指现在。)
If someone tried to blackmail me I would tell the police.
如果有人企图敲诈我,我就向警察告发。(但我想不会有人敲诈我。句子的含义是指将来。)
第一类和第二类条件句之间并不存在时间上的差别。像第一类条件句一样,第二类指的是现在或将来; if从句中的过去时不是真正的过去时,只是一?#20013;?#25311;语气,表示不真实(如上述第一个例子)或不大可能(如上述第二个例子)。
类型2有以下用法:
1.所假设的事与已知的事实相?#35789;保?/strong>
If I lived near my office I’d be in time for work.
要是我住的离办公楼近,我?#20064;?#23601;不会迟到。(但我不住在办公楼附近。)
If I were you I’d plant some trees round the house.
如果我是你的话,我就会在房子周围种一些树。(但我不是你。)
2.说话人认为从句中的动作不会发生时:
If a burglar came into my room at night I’d scream.
要是半夜三更窃贼闯进我的?#32771;洌?#25105;就会拼命叫喊。(但我不认为会有窃贼闯入我的?#32771;洹#?/div>
If I dyed my hair blue everyone would laugh at me.
要是我把头发染成蓝色,大家就要笑我了。(但我不想染它。)
有些if从句可?#26434;?#19978;述两种含义中的一种:
If he left his bicycle outside someone would steal it.
要是他把自行车放在外面,会有人把它偷走。
If he left his bicycle可以意指可他没有(如上述 1中的用法,指的是现在)或他没这么打算(如上述2中的用法,指的是将来)。但真正的含义通常从上下文中可以看清楚。
这种语义混淆可以通过使用were/was+不定式而不用上述类型2中的一般过去时来避免。
if he/she/it were可?#28304;?#26367; if he/she/it was,而且被认为是更正确的形式:
If he were to resign…相当于:
If he resigned…
他万一(果真)要辞职的话……
If I were to succeed…相当于:
If I succeeded…
我竟然(果真)会成功的话……
were的这种用法主要见于相当正式的句子里。
if he/she/it was+不定式在日常口语中是可以的,但是如上例所示那样使用过去时态更为常见。
3 .有时类型2可?#26434;?#20570;类型1的替代形式,表?#23601;?#20840;有可能实现的计划和建议。这种用法颇易引起混淆:
—Will Mary be in time if she gets the ten o’clock bus?
—No, but she’d be in time if she go the nine-thirty bus./No, but she’ll be in time if she gets the nine-thirty bus.
—如果玛丽赶上10点钟的公共汽车,她会及时到达吗?
—不会的,但是如果她赶上9点30分的汽车,她就会及时到达。
—We’ll never save£ 100!
—If we each saved£ 10 a week we’d do it in ten weeks./If we each save £10 a week we’ll do it in ten weeks.
—我们永远攒不了100英镑!
—要是我们每人每周储蓄十英镑,我们在十周后就会做到。
以类型2的形式表示建议要比以类型1的形式有礼貌些,就如同用would you表示要求要比will you更有礼貌一样。但学生不必在类型2的这种用法上花过多工夫。
基本形式可能的变化形式
1.主句的变化
(a)可?#26434;胢ight或could而不用 would:
If you tried again you would succeed.
要是你再试一试,你会成功的。(可靠的结果)
If you tried again you might succeed.
要是你再试一试,可能会成功。(可能的结果)
If I knew her number I could ring her up.
要是我知道她的号码,就能给她打电话。(能力)
If he had a permit he could get a job.
要是他有许可证的话,就可以找到工作。(能力或允许)
(b)可?#26434;?#26465;件时态中的进行时而不用其一般时:
—Peter is on holiday;he is touring Italy.
—If I were on holiday I would/might be touring Italy too.
—?#35828;?#22312;休假,他在意大利旅游。
—如果我在休假,我?#19981;幔?#21487;能)在意大利旅游。
(c)希望表达过去自动的或习惯性的?#20174;?#26102;,可以在if+过去时后再跟一个过去时。注意:这里的过去时具有过去的含义:
If anyone interrupted him he got angry.
如果有人打扰他,他就会生气。(每当有人打扰他时)
If there was a scarcity of anything,prices of that thing went up.
如果什?#27425;?#21697;短缺,那种物品的价格就会上涨。
(d)当if用来表示as或since的时候,主句中可能用各种时态。这里if+过去时态具有过去的含义。这种句子并不是真正的条件句。
—The pills made him dizzy.All the same he bought/has bought/is buy-ing some more.
—If they made him dizzy why did he buy/has he bought/is he buying more?

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