Is this a question tag - "did they"?

[Priyanka]

Test No. incompl/elem-35 "Question Tags", question 10

No-one understood that word .........

(a) does he?
(b) did you?
(c) didn't they?
(d) did they?

Test No. incompl/elem-35 "Question Tags", answer 10

No-one understood that word did they?

Correct answer: (d) did they?

Your answer was: incorrect
No-one understood that word did you?
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in the 10th answer why do you say 'did you'?

[Torsten]

Hi Priyanka,

As you can see the correct answer here is (d) did they?
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Test Of English for International Communication
TOEIC Preparation & TOEIC Vocabulary