Vintage year - first drawdown or when all drawdowns are completed

Hi what is a vintage year

A) When you take the first drawdown?

B) when you close a fund i.e. receive all committed capital

C) When p/e firm makes an investment in a portfolio company once it collects requisite funds for that investment but the overall fund is not yet closed i.e. all comitted cap is not recd

D) any other rocket science

Pls help?

?

Any one pls