Question

3) They were planting trees into passive voice
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Answer 1

The trees were being planted by them.

Step-by-step explanation:

You have to first find the subject then start you sentence with it

Answer 2

Trees were planted by them.

Step-by-step explanation:

Passive voice tells us what is done to someone or something.

{Object + verb + subject}

Trees (object) + planted (verb) + them (subject) = Trees were planted by them.

Hope this helps :)