Rewrite the following sentences into the passive voice 1. they are writing a test now. 2. they did not turn off the light 3. i have invited some friends to tea 4. have you written the letter yet? 5. snow will cover the fields

1 A test is written by them now 
2 The light wasn't turned off by them 
3 Some friends have been invited to tea by me
4 Has the letter been written yet by you? 
5 The fields will be covered by snow