下面是关于Jim学习英语的三对句子。每对句子中,第一句是原句,第二句是对第一句的改写,要求根据原句和第二句中已经给出的部分用一至五个单词补全第二句。(注意,不能改变原句的意思。)

James Watt()the steam engine.

A.was inventing

B.invented

C.had invented

D.has invented

Professor White contributed a lot to our community,().

A.teaching,writing,and lecturing

B.teaching,writing,and alecturer

C.a teacher,a writer,and lecturing

D.teaching,lecturing,and a writer

On my left()a wide river;on my right,a dark forest.

A.has been

B.was

C.are

D.would be

The firemen tried their best to()the fire but in vain.

A.put up

B.put forward

C.put down

D.put out