Step 1: Understanding the sentence meaning.
The question “..........you decided yet?” implies that the decision-making process might have already happened, but the speaker is checking if it is complete. This suggests the use of the **present perfect tense**.
Step 2: Grammar rule.
The structure of a present perfect question is:
Have/Has + subject + past participle (V3)
Since the subject is “you,” the correct auxiliary verb is **“have.”**
Step 3: Analyzing the options.
- (a) Has: Used with singular subjects (he/she/it), not with “you.” Incorrect.
- (b) Do: Used in simple present tense questions (e.g., Do you like?). Incorrect here.
- (c) Did: Used in simple past tense (e.g., Did you decide yesterday?). The word “yet” indicates present perfect, not past.
- (d) Have: Correct, as it matches with “you” in present perfect form.
Step 4: Constructing the sentence.
The correct question is: “Have you decided yet?”
Step 5: Conclusion.
Thus, the correct auxiliary verb to complete the sentence is “have.”