Here are the correct choices for each sentence:

1. **Last Monday when I ___ the house it ___ heavily.**
- **Answer:** B) left / was raining

2. **Yesterday when Tom ___ the lesson ___.**
- **Answer:** C) came / already began

3. **___ the call because I ___ a shower.**
- **Answer:** A) didn’t answer / was taking

So the completed sentences are:

1. Last Monday when I **left** the house it **was raining** heavily.
2. Yesterday when Tom **came** the lesson **already began**.
3. **I didn’t answer** the call because I **was taking** a shower.