1. B. telephone

2. B. aviation

3. D. 25

4. A. Bell was born in the 18th century. 

5. B. He dedicated his lifebto science and the well-being of mankind. 

5 x 6= 30 . Vậy số đó là ( 30 + 12 ) = 42

1. A sudden increase in water  pressure may break the dam.

=> The dam may be broken by a sudden increase in water pressure.

2. For the past years i have done all my washing by hand.

=> For the past years, all my washing have been done by hand.

3. A man i know told me about it.

=> I was told about it by a man I know.

4. The teacher returned our written work to us.

=> Our written work were returned to us by the teacher.

5. She had finished her report by soon.

=> Her report had been finished soon.

6. This is the second time they have writtten to us about this

=> This is the second time we have been written to about this.

7. The boys broke the window and took away some pictures

=> The window was broken and some pictures were taken away by the boys.