SINCE o FOR

My sister has stopped smoking _________ the 10th of May.
1. since
2. for
These eggs have been in the fridge ________ twenty days.
1. since
2. for
We have kept this computer _______ 1991, and it still works!
1. since
2. for
He has been a teacher at this school ________ many years.
1. since
2. for
They've been married ________ thirty years.
1. since
2. for
Henry has played basket ________ he was eight years old.
1. since
2. for
Bob has been here ________ 4 o'clock.
1. since
2. for
I have lived in Germany ________ last April.
1. since
2. for
It has snowed ________ five hours today.
1. since
2. for
Mary has been a professional guitar player ________ 1989.
1. since
2. for