Answer:
I was going to be late for band practice therefore, I decided to bring the band director a cookie.
Suppose
Here's a link to help you further
http://writingexplained.org/suppose-vs-supposed-difference
The definition of communal is "Shared by all members of a community; for common use."
I would say that their kitchen <em>is</em> communal because their "community" consists of all the roommates who use the kitchen and contribute to it. If only one person contributed to the kitchen stock, then it would not be communal.
