Complete the sentences with the Past Continuous or the Past Simple form of the verbs. Who do you think is talking?

1. In the morning, Pi was playing (play) a game on the lab computer when I came (come) in!

Explanation: 'was playing' is in Past Continuous because it describes an ongoing action in the past. 'came' is in Past Simple because it describes a completed action that interrupted the ongoing one.

2. Then, Millie and I were working (work) in the lab when the lights went (go) out.

Explanation: 'were working' is in Past Continuous because it describes an ongoing action in the past. 'went' is in Past Simple because it describes a completed action that happened during the ongoing one.

3. After lunch, Rob and I were listening (listen) to my favourite opera when the speakers broke (break).

Explanation: 'were listening' is in Past Continuous because it describes an ongoing action in the past. 'broke' is in Past Simple because it describes a completed action that interrupted the ongoing one.

4. But in the evening, I was painting (paint) a picture when I had (have) a fantastic idea! What a day!

Explanation: 'was painting' is in Past Continuous because it describes an ongoing action in the past. 'had' is in Past Simple because it describes a completed action that happened during the ongoing one.

The speaker is likely Rob, as he is mentioned in sentence 3 in relation to listening to opera. However, the question is subjective and could refer to any of the individuals mentioned if they were the one sharing the experience.