被动语态的运用

什么情况下要用被动语态呢?一般地说，有下面几种情况：

(1) 不知道谁是动作的执行者或没有必要。例如：

Paper is made from wood. (纸是由木材生产出来的。)

The house is quite old. It was built in 1950. (这座房子太旧了。它是1950年建成的。)

he was wounded in the fight. (他在战斗在受伤了。)

Electricity is used to run machines. (电是用来开动机器的。)

(2) 需要强调动作的对象时。例如：

Calculator can t be used in the maths exam.

(计算器不能用于数学考试。)

Books and newspapers in the reading room mustnt be taken away. (阅览室的书籍和报纸不准带走。)

he was awarded first prize in that contest.

(他在比赛中获得了第一。)

(3)为了使语气婉转，避免提到是谁做的这件事。例如：

The construction of the new lab must be completed by the end of next month. (新实验室必须在下个月底前完工。)