Question

passive voice
Water covers most of the Earth's surface.
Have you painted the room?
We must do something to avoid problems.
They have built a new hospital near the airport this year.
They don't advise us to go there so often.

Answer 1

Most of the Earth's surface is covered with water.
Has the room been painted by you?
Something must be done by us to avoid problems.
A new hospital has been built near the airport this year.
We aren't advised to go there so often.