The Dictionary of Occupational Titles relates all vocational interests to:

1 things

2 data

3 people

4 all of these

4. all of these ...

The correct answer is 3. People.

Explanation:

The DOT, is a publication of the various types of what and what each of them involve. Later on, it became obsolete and was replaced by an online database, which people with direct experience input the appropriate information. In this case, the missing word is people.

The DOT relates all vocational interest to people; as data an things cannot feel interest.