Q1. The book __________ (be leave) on the table when I left the classroom.

Q2. This building __________ (be build) 20 years ago.

Q3. The cake __________ (be make) by my mother not long ago. Let's try!

Q4. Tom __________ (be bite) by a dog just an hour ago, so he is in hospital now.

5 answers

http://examples.yourdictionary.com/examples-of-active-and-passive-voice.html
Read and study this webpage so you understand the differences in how active voice verbs are phrased from how passive voice verbs are phrased.

I'll do the first one here for you. Then you try the rest, and we'll check your work for you.

Q1. The book was left on the table when I left the classroom.

Q2. This building was built (be build) 20 years ago.

Q3. The cake was made(be make) by my mother not long ago. Let's try!

Q4. Tom was bitten (be bite) by a dog just an hour ago, so he is in hospital now.

All three are right.

Nice!

Thanks so much!

You're welcome.