Fill in the gaps using who, whose, which, where, when, why

The boy ... mother worked at the swimming pool could attend it free.
This season of the year reminds me of the time ... we met.
She understood ... I had changed my mind to go swimming.
I don’t see anybody ... I can ask for help.
It was the book ... had been given to me by my great-grandmother. It’s the street ... I used to live many years ago.