correct responses

In the last response, "So she is" makes it sound like you didn't realize she was your own sister. "So it is" is more appropriate.

Thanks, SCoates.

Just to confirm: The other responses are correct.

Essentially. The primary concern is that the question is improper, refering to students as "that" or "it." So I think it would be acceptable either way. However, your choices are more proper.

The simplest guidance is to say that if the question is expressed impersonally, you MUST make the answer match.

Is that your student?
Yes, it is.

That is your student, isn't it?
Yes, it is.

Is that Jim, your student?
Yes, it is.


That's your sister, look!
So it is!

--- but ---

Is Jim your student?
Yes, he is.

Jim's your student, isn't he?
Yes, he is

Is Mary your sister?
Yes, she is.

Many thanks, Contrex.

Well, not MUST necessarily. These would represent a normal neutral reply but other replies are certainly possible, including less than a full response.

Is that your student?
Yes / Uh-huh / Yup / Yeah

Jtt, did you appreciate the question Yoong Liat was actually asking?

Perfectly, Contrex.