Explanation:

To find the correct one word substitution for the sentence People living at the same time, we need to check the meanings of all options given below.

1. contemporaries - a person or thing living or existing at the same time as another.

2. cosmopolitans - including people from many different countries.

3. comrades -  a colleague or a fellow member of an organization.

4. friends - a person with whom one has a bond of mutual affection, typically one exclusive of sexual or family relations.

Hence, it is clear from the above analysis that option 1 is the correct answer.