Active Voice: He (to write) writes books.

Passive Voice: The A lot of questions (to discuss) are discussed every day.
1)Every two years the boiler also (to have to) ответ
be inspected and certificated.
2)During this inspection a number of tests (to take place) ответ
.
3)The machine (to disconnect) ответ
from the water circuit.
4)Then the boiler (to put) ответ
under a pressure of 25 bars.
5)The thickness of the boiler wall (to measure) ответ
with the help of x-ray device.
6)Every month there also a number of other tests (to have to) ответ
be done by the personnel of the Housing Service.