Here are the best answers for each question:

1. **B**. was going - were cooking
(The fire alarm interrupted the ongoing activity of cooking.)

2. **C**. was fixing - was reading
(Indicates simultaneous actions in past continuous.)

3. **B**. was raining - were arriving
(Describes two actions happening at the same time in the past.)

4. **A**. were telling - went
(Indicates a continuous action interrupted by another action in the past.)

5. **A**. was waiting - saw
(Describes an action happening when something else occurred.)

So the final answers are: 1B, 2C, 3B, 4A, 5A.