multiple post passwords plugin password expiry

Can you clarify the meaning of “Expire passwords after x hours”, does it mean
a) the password will expire forever and no one will be able to use it after the time set,
b) the password will expire for the person who entered it and they won’t be able to use it again after the time set but other people would,
c) it would time out and anyone who used it before would have to re-enter it after the time set to access the protected page