1. first aid

　　（1）n.（对伤患者的）急救

　　give first aid to sb.= carry out first aid on sb.对某人实施急救

　　拓展：aid n.帮助， 援助， 帮助者，有帮助的事物

　　cut off aid中止援助

　　teaching aids教具

　　a hearing aid助听器

　　medical aid医疗救护

　　with the aid of借助于= with the help of

　　come to sb.'s aid帮助某人

　　in aid of为了帮助

　　we collect money in aid of the education in the poverty-stricken area. 我们筹集资金以援助贫困地区的教育。

　　（2）vt.资助， 援助， 帮助

　　I aided him in his enterprise.

　　They aided in solving the problem.

　2. a number of adj."许多的， 若干"后接可数名词

　　区别：the number of / a number of：

　　都跟可数名词复数。前者作主语，谓语用单数；后者作主语，谓语用复数。

　　The number of the trees is two thousand. （用单数谓语. 另注意trees前有限定词）

　　A number of trees have been cut down. （用复数谓语. 另注意trees前无限定词）

　　拓展：

　　后接可数或不可数名词的短语：

　　1）lots of（a lot of）后接可数或不可数名词。例如：

　　My parents spend a lot of their spare time on English study.

　　Mike had collected lots of Chinese stamps when he studied in China.

　　2）plenty of后接可数或不可数名词。例如：

　　We have plenty of books to read.

　　There is plenty of water in apple.

　　（注：plenty of一般只用于肯定句，在疑问句中常改用 enough；在否定句中常改用 many或 much。另外， plenty of短语作主语时，谓语动词的数由它后面的名词的数而定。）

　　3）most of后接可数或不可数名词。例如：

　　Most of his money is spent on books.

　　Most of the students in our class are fond of sports.

　　4）a large quantity of后接可数或不可数名词。例如：

　　A large quantity of books have been translated into foreign languages.

　　There is a large quantity of coal in the coal－mine.

后只接可数名词的短语

　　1）a group of后接可数名词的复数。例如：

　　A group of wounded soldiers were saved by Dr Bethune.

　　2）a（great/large/good）number of后接可数名词的复数。例如：

　　There are a number of professors in our college.

　　A great（large／good） number of new machines have been sent to the country side.

3）a great many后接可数名词的复数。例如：