Question

-Are these your rulers?

-________.

1. A.
   Yes, they're
2. B.
   Yes, they aren't
3. C.
   No, they're
4. D.
   No, they aren't

Answer 1

D
A项若是Yes, they are。才对。而they're是肯定句的缩写式，后面还应有名词/代词/形容词等才行，如：They're boys. They're fine.等，否则不能用在简略答语中。