Step 1: Recall the nature of structured questions.
They are fixed-response, making coding easy and analysis faster — this is actually an advantage, not a disadvantage.
Step 2: Review real disadvantages.
- (b) Requires careful design to cover all possible responses clearly.
- (c) Pre-listed options can bias answers (framing effect).
- (d) Limits ability to capture unexpected answers.
Step 3: Identify the “not a disadvantage” option.
- (a) describes an advantage, so it is correct here.
\[
\boxed{(a)}
\]