英语时态问题

Question

It seems oil__from this pipe for some time.we'll have to take the machine apart to put it right.
A.had leaked B.is leaking C.leaked D.has been leaking
这是个时态题！怎么做，答案是D

Answer 1

先看状语：for some time 一段时间
表示从过去某时开始一直持续到现在的动作，并且还将持续下去，所以用现在完成进行时。

以下供参考：

现在完成进行时的谓语动词构成
I/ we/ you/ they have been doing sth.
he/ she/ it has been doing sth.
（一）表示从过去某时开始一直持续到现在的动作，并且还将持续下去。
The Chinese have been making paper for two thousand years.
中国有2000年的造纸历史。（动作还将继续下去）
I have been learning English since three years ago.
自从三年前以来我一直在学英语。（动作还将继续下去）
（二）表示在说话时刻之前刚刚结束的动作。
We have been waiting for you for half an hour.
我们已经等你半个钟头了。（动作不再继续下去）
（三）有些现在完成进行时的句子等同于现在完成时的句子。
They have been living in this city for ten years.
They have lived in this city for ten years.
他们在这个城市已经住了10年了。
I have been working here for five years.
I have worked here for five years.
我在这里已经工作两年了。
（四）大多数现在完成进行时的句子不等同于现在完成时的句子。
I have been writing a book.（动作还将继续下去）
我一直在写一本书。
I have written a book.（动作已经完成）
我已经写了一本书。
They have been building a bridge.
他们一直在造一座桥。
They have built a bridge.
他们造了一座桥。
（五）表示状态的动词不能用于现在完成进行时。
I have known him for years.
我认识他已经好几年了。
* I have been knowing...
这类不能用于现在完成进行时的动词还有：love爱，like喜欢，
hate讨厌，等。
比较过去时与现在完成时
1）过去时表示过去某时发生的动作或单纯叙述过去的事情，强调动作；现在完成时为过去发生的，强调过去的事情对现在的影响，强调的是影响。
2）过去时常与具体的时间状语连用，而现在完成时通常与模糊的时间状语连用，或无时间状语。
一般过去时的时间状语:
yesterday, last week，…ago, in1980, in October, just now, 具体的时间状语
共同的时间状语:
this morning, tonight,this April, now, once，before, already, recently，lately
现在完成时的时间状语
for, since, so far, ever, never, just, yet, till / until, up to now, in past years, always,
不确定的时间状语
3）现在完成时可表示持续到现在的动作或状态，动词一般是延续性的，如live, teach, learn, work, study, know.
过去时常用的非持续性动词有come, go, leave, start, die, finish, become, get married等。
举例：
I saw this film yesterday.
（强调看的动作发生过了。）
I have seen this film.
（强调对现在的影响，电影的内容已经知道了。）
Why did you get up so early?
（强调起床的动作已发生过了。）
Who hasn't handed in his paper?
（强调有卷子，可能为不公平竞争。）
She has returned from Paris.
她已从巴黎回来了。
She returned yesterday.
她是昨天回来了。
He has been in the League for three years.
(在团内的状态可延续)
He has been a League member for three years.
(是团员的状态可持续)
He joined the League three years ago.
( 三年前入团，joined为短暂行为。)
I have finished my homework now.
---Will somebody go and get Dr. White?
---He's already been sent for.
句子中如有过去时的时间副词（如 yesterday, last, week, in 1960）时，不能使用现在完成时，要用过去时。
（错）Tom has written a letter to his parents last night.
（对）Tom wrote a letter to his parents last night.
过去完成时
1） 概念：表示过去的过去
----|-------|-----|---->其构成是had +过去分词构成。
那时以前 那时 现在
2） 用法
a. 在told, said, knew, heard, thought等动词后的宾语从句。
She said (that) she had never been to Paris.
b. 状语从句
在过去不同时间发生的两个动作中，发生在先，用过去完成时；发生在后，用一般过去时。
When the police arrived, the thieves had run away.
c. 表示意向的动词，如hope, wish, expect, think, intend, mean, suppose等，用过去完成时表示"原本…，未能…"
We had hoped that you would come, but you didn't.
3) 过去完成时的时间状语before, by, until , when, after, once, as soon as。
He said that he had learned some English before.
By the time he was twelve, Edison had began to make a living by himself.
Tom was disappointed that most of the guests had left when he arrived at the party.
现在完成进行时 :
其构成形式如下：
I / we / they have
He / she / it has been + 动词的现在分词
功用如下：
1） 表示一个在过去开始而在最近刚刚结束的行动，如：
Ann is very tired. She has been working hard.
Why are you clothes so dirty? What have you been doing?
2) 表示一个从过去开始但仍在进行的行动，如：
It has been raining for two hours. (现在还在下)
Jack hasn’t been feeling very well recently.
3) 表示一个从过去开始延续到现在，可以包括现在在内的一个阶段内，重复发生的行动，如：
She has been playing tennis since she was eight.
4) 现在完成时强调动作行为的结果、影响，而现在完成进行时只强调动作行为本身，如：
Tom’s hands are very dirty. He has been repairing the car.
The car is going again now. Tom has repaired it.
注意：
•
现在完成时有否定结构、而现在完成进行时没有否定结构。
现在完成时态可表示做完的时期以及已有的经验、但现在完成进行时不可以