Grammar

[Anna3627]

Which is correct:
"it is the first time sb have done sth"
or "this is the first time sb have done sth"?

[meltoadhall]

neither "have done" is not correct, try "has done" or "did" depending on who did what and when

[Gef]

Question makes no sense unless we know whether sb is singular or plural.

sb, sth are not in my dictionary.

[rosepetal]

Gef - I think sb stands for somebody and sth stands for something.
Both of these abbreviations are in the Cambridge online dictionary.

[Anna3627]

Sorry I didn't make it clear. Now look at this:
Question 1 It is the first time I ___ a koala.
A. have seen B. see C. saw

Question 2 This is the first time I ___ a koala.
A. have seen B. see C. saw

Please choose all the possible answers.

I remember either 'it is the first time' or 'this is the first time' must be followed by "somebody have/has done something". But I can't remember clearly.

Any answer is appreciated.

[taichiperson]

It would be

It is the first time somebody has done something
This is the first time somebody has done something
but
It is the first time I have seen a koala
This is the first time I have seen a koala

It comes down to 'I have', but 'He/she has' or 'they have' etc