在英语越来越重要的21世纪，学好英语成了大学生的首要目标。为帮助大学生更好地掌握英语知识，特提供以下文章：
Agriculture is the country's chief source of wealth, wheat _____ by far the biggest cereal crop.
A. is
B. been
C. be
D. being
Key: D
本题考的是独立主格结构。
我们要来复习的就是独立主格结构.
1)名词/代词+分词
The foreign travelers had many talks with the natives, the guide acting as an interpreter .
He being absent, nothing could be done.
The floor being wet and slippery , we stay outside.
All things considered, I think I ought to award the job to Mrs. Smith.
•1. 独立主格结构的语法形式是：主语+非谓语动词。
•2. 非谓语动词有三种：(1)to+v.
• (2)v. –ing
• (3)v. –ed
•3. 非谓语动词的特点：
•1) 时间关系：
• (1) 不定式具有后时性
• (2) –ing 分词具有同时性
• (3) –ed 分词具有先时性
e.g. Here are the first two volumes, the third one to come out next month.
They visited Danxia Mountain yesterday, Miss Lee acting as the tourist guide.
His work done, he went home.
2)逻辑主语与非谓语动词的关系：
(1) –ing分词表主动
(2) –ed分词表被动
e.g. He being sick in bed, the team had to find a replacement.
Weather permitting, we will go picnicking this weekend.
The friendly match being over, the players of the two countries shook hands with each other.
All the tickets sold out, they returned home disappointed.
The dispute settled, the meeting came to an end.
His voice drowned by the noise, the speaker interrupted his lecture.
现在你对独立主格的结构了解多少呢?
(1) 找出非谓语动词的逻辑主语
(2)弄清楚非谓语动词与逻辑主语的主被动关系
(3) 弄清楚非谓语动词与主句动词的时间关系