`III.`

`text{1.The problem of energy shortage will be solved by using solar energy.}`

`text{2.It is interesting to travel around the world.}`

`text{3.I haven't seen Hoa since 2012.}`

`text{4.This building was built 2 years ago.}`

`IV.`

`text{1.Hung's Temple was visited by my class last week.}`

`text{2.Lan didn't go to school because she was ill yesterday.}`

`text{3.It took me 30 minutes to go to the airport.}`

`text{4.If you are not careful,you'll hurt yourself.}`