Grammar: Perfect Tense & Connectives(语法：完成时和关联词)
1. 完成时
1. 1 现在完成时 (Present perfect Tense) 的构成及用法：现在完成时由助动词have (has) + 动词的过去分词构成。
1) 过去某动作到现在已经完成或刚完成， 或对现在产成了结果。
I have finished the editing of my book.
The have built many factories in China in the past 10 years.
2) 动作在过去发生但一直延续到现在。
How long have you been in Edmonton?
I have made many friends since I came to Canada
现在完成时的时间状语问题：
1) 现在完成市属现在的范畴，不能和表示过去的某一具体时间状语连用， 如：yesterday, last week, two days, in 1990 …等。
The Second World War began in 1941.
The Second World War has begun in 1941.
2) 现在完成时常和表示不确定的时间副词连用，如：already, often, never, ever, always, yet, just …等。
Have you ever been to rural areas?
The children have already done with their eating.
3) 可以和包括现在在内的时间状语连用， 如：now, today, this month …等。
Today I have made thirteen paper planes.
Now everyone has expressed his opinion.
1. 2 过去完成时 (Past perfect Tense) 的构成及用法：由助动词 had + 动词的过去分词构成。
1) 表示某一动作在过去某一特定时间以前就完成了，即“过去的过去”，句中常有by, for, before 等时间短语或从句。
By the end of last month, 109 experts had been sent to that area.
I have never gone to the nightclub before I met him.
2) 表示由过去某一时间的动作一直延续到过去另一时间，句中常有by, for, since 等短语或since, after 等引导的从句。
It rained yesterday after it had been dry for many months.
By the time he settled in France, he had visited 29 countries.
1. 3 将来完成时 (Future Perfect Tense) 的构成及用法：表示在将来某一时间以前已经完成的动作。 有should (第一人称)或will (第二、三人称) + have + 动词的过去分词构成。
By the end of this semester, we shall have learned 20 lessons.
When you come back tonight, I shall have finished the thesis.
1.4 过去将来完成时(Future-in-the-past Perfect Tense) 的用法：表示在过去某一时间以前已经完成的动作。由should (第一人称) 或would (第二、三人称) + have + 动词的过去分词构成。
I hoped that when we arrived there they would have made everything ready.
He did not go for believing that the wedding would have already been finished when he arrived, but actually it lasted from morning to night
2. 关联词 (Connective)
有些地方称并列连词 (a word or phrase whose function is to link other linguistics units)。其特点是关联词 (并列连词) 前后的句子成分在语法上是平行的。 常用的并列连词有：and, as well as, but, yet, however, therefore, so, or, nor, neither … nor …, either … or …, both … and ……等。
Examples:
It was cold and he had no money to buy food.
It rained heavily last night, but I still went to the church.
The working good, yet it could have been better.
You must se aside time for work as well as play.
Hurry up, or you will be late.
I never saw him nor heard from him again.
You may write the letter either in ink or in blood.
Both you and I are invited to the party.
The book is due tomorrow. Therefore, you must finish it today.
My sister-in-law enjoys pop music. So does my younger brother.
He cannot speak Italian. Nor can I.
She can play basketball and piano as well.