I confront the following situation so often in many different cases:

Assume that I want to write about the cars of two persons, then which of the followings is correct?

- I asked them about the model of their cars.
- I asked them about the models of their cars.
Generally, should I use plural or single form when I want to refer to a quality/characteristic related to different things/persons?

**Answer**

There are several possibilities here.

The first group of possibilities is that you asked each person on their own, one at a time.

1. Each person has a single car.

I asked each of them about the model of their car.

2. Each person has multiple cars. (Or you don’t know how many cars each of them has.)

I asked each of them about the models of their cars.

The second set of possibilities is that you asked them together, as a group. Or you use ambiguous phrasing where it’s not clear if you asked them on their own or together.

3. Each person has one or more cars. Between all the cars of both people, there are at least two different models. (Or you don’t know how many or what models the two of them have.)

I asked them at the same time about the models of their cars.

I asked them about the models of their cars.

4. Each person has one or more cars. Between all the cars of both people, the cars are the *same* model.

I asked them at the same time about the model of their cars.

I asked them about the model of their cars.

**Attribution***Source : Link , Question Author : Bob , Answer Author : Jason Bassford*