1)单数名词加s: students, apples, bags, trees, books, brothers.

2)以s、x、sh、ch结尾的名词加es: glasses, boxes, brushes, matches.

3)以辅音字母加y结尾的名词，变y为i加es: cities, babies, enemies.4)以f或fe结尾的名词，多数变f为v加es: wives, knives.但有些词只加s: roofs, proof s, chiefs.

5)以o结尾的名词，有些加es: Negroes, heroes, tomatoes, potatoes.其它加s: radio s, zoos, pianos, photos.

6)不规则名词：foot→feet, goose→geese, tooth→teeth, child→children, man→me n, woman→women, sheep→sheep, deer→deer, mouse→mice.

7)某些外来词变复数：datum→data, medium→media, bacterium→bacteria, curriculum→curricula, criterion→criteria, phenomenon→phenomena. (um/on→a)analysis→analyses, basis→bases, crisis→crises, diagnosis→diagnoses.(is→es )

8)复合名词变复数：以不可数名词结尾的复合名词无复数形式，如：homework.

以man或woman为前缀的复合名词变复数，前后两个名词都变复数，如：manservant→menservants, woman student women students.

其它复合名词变复数：grownup→grownups, brotherinlaw→brothersinlaw, standby→standsby.

9)复合形容词做定语时，其中的名词保持单数：a sixyearold boy，a twohundredpage book

【例句】A second doctor must confirm that these criteria ______ and the death must be re ported to the police department.

A) has been met

B) have been met

C) was met

D) was being met

criteria是复数形式，故A，C，D都为错误选项。正确答案为B。

1) The university authorities are seriously considering abandoning the traditional______class.

A) fifth minutes

B) fiftyminutes

C) fiftyminute

D) fifty minute's

复合形容词用作定语时，其中的名词不变复数，故B不对。A不能做定语，D应为fifty minutes'，正确答案为C。