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That is the last bus, isn't it?

That is Tom, isn't it?

Are those question tags all correct? Especially the second one, is it true to use "it" to refer to somebody? Thank you for your explanation!
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Both correct.

See at the BBC:

http://www.google.com/search?hl=en&q=site%3Abbc.co.uk+%22him+isn%27t+it%22+&btnG=Google+S...

It
is used not to refer to somebody, but to the situation, meaning:

Is the situation the way I described it?
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Marius Hancu
It
is used not to refer to somebody, but to the situation, meaning:

Is the situation the way I described it?

Wow. What a good explanation! Thanks Marius. Emotion: smile
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Comments  
the second one should be "isn't he?" I also want to know.
 Marius Hancu's reply was promoted to an answer.
Marius HancuBoth correct.

See at the BBC:



It
is used not to refer to somebody, but to the situation, meaning:

Is the situation the way I described it?

I'm glad to see this explanation, as I otherwise wouldn't have been able to defend my natural choice of 'it', which I prefer not to use with people.
Students: We have free audio pronunciation exercises.
 Doll's reply was promoted to an answer.