A question goes:
A:Look! Isn't that Judy?
1) That isn't.
2) It isn't.
The given answer is (2).
What's wrong with (1)?
Practical English Usage, by Michael Swan.
this/that and it:
things that have just been mentioned
1 referring back
This, that and it can all be used to refer back thing or situations that have just been talked or written about. It does not give any special emphasis.
According to this, I think (1) could also be used in the reply.
If you think about it, the "it" could be seen as referring to the truth value of the implied statement '[That is Judy]'; it refers back to the words 'Look, isn't that Judy?' but not (in a possible interpretation) to the object/person indicated.
Both 'that' and 'she' could be used, but in different contexts:
- 'That's a car, isn't it?'/'No, that isn't, but there is one over there.'
- 'That's Judy, isn't it?'/'No she isn't, but she is'
(In both cases the speaker indicates a different thing/person from the one that the first speaker pointed at.)
Last edited by BobK; 19-Dec-2008 at 11:48. Reason: Corrected original statement (to match OP)