Bob uses illicit drugs "socially". His use does not produce problems with his social, educational, or occupational functioning. Bob's behavior constitutes:

a. substance withdrawal

b. substance use

c. substance intoxication

d. a substance use disorder

b. substance use

Explanation:

Substance use refers to the use of drugs or cigarettes, alcohol, or anything like that. It basically turns into an addiction and that is when the problem starts.

This further creates a problem in terms of health issues with the person concerned, although there might not be any chance of destruction or poor performance in his academic or social well being.

It basically develops a tendency in person, that the person starts thinking that he would not be able to survive without those illicit drugs.

In the given instance also, Bob is developing substance use.