Explanation:

- "Junkie" is a slang term commonly used to refer to someone who is addicted to drugs, particularly illegal ones. It often carries a negative connotation.

- Option 1: "Joker" refers to someone who jokes or a card in a card deck. It is not a synonym for "junkie."

- Option 2: "Drug addict" is the closest synonym to "junkie" as it directly refers to someone who is addicted to drugs.

- Option 3: "Useless" means not serving any useful purpose or not effective. It does not relate to "junkie."

- Option 4: "An inferior workman" refers to someone who lacks skills or competence in their work. It doesn't align with the meaning of "junkie."