Question

when a policeman ...... (approach)them,they were all (sit) in car .use correct form of verb

Answer 1

The correct use of verb forms is as given below:

When a policeman approached them, they were all sitting in car.

Explanation

We use the past simple for a complete action in the past. We use the past continuous for an action that we were in the middle of. We often use the past continuous and simple together when one (shorter) action comes in the middle of another (longer) one. The policeman approached (shorter action) in the middle of the longer action (sitting in the car).