Explanation:

- Option 1: have bought

- Present perfect tense.

- Used for actions completed at some indefinite time in the past.

- Not suitable as the specific time is mentioned (five years ago).

- Option 2: bought

- Past simple tense.

- Used for actions completed at a specific time in the past.

- Perfect fit since "five years ago" refers to a specific time.

- Option 3: has bought

- Present perfect tense.

- Generally used with he/she/it.

- Incorrect subject-verb agreement for "I."

- Option 4: buy

- Present simple tense.

- Used for habitual actions or general truths.

- Not suitable here.

---