Step 1: Understanding the helping verb “Did.”
When a question begins with “Did,” it is in the simple past tense. After “Did,” the main verb must always appear in its base form (V1), not in the past or continuous form.
Step 2: Analyze the options.
- (a) choosing: Present participle — incorrect.
- (b) choose: Base form (V1) — correct form after “Did.”
- (c) chooses: Present tense (used with singular subjects) — incorrect.
- (d) chose: Past tense (V2) — incorrect because “Did” already makes the verb past.
Step 3: Grammar rule.
Structure: “Did + subject + base form (V1).”
Example: “Did you go?” / “Did he play?”
Step 4: Constructing the correct sentence.
“Did you choose this colour?”
Step 5: Conclusion.
Hence, the correct option is (b) choose.