"Coffee" answers

(If you've come here wondering what this is all about, the post this refers to can be found here.)

As I said here are the answers for the "Coffee" grammar exercise. If you aren't a native speaker of English these exercises can be quite difficult.
1) which 2) were 3) could 4) to 5) become 6) until 7) first 8) had 9) how 10) where 11)because 12) on 13) their 14) for 15) the