C Fill in the gaps with who, which, where, why or when.
14 Do you know the reason _____ she is so upset?
15 The library is a place _____ you can borrow books.
16 The day _____ you saw me I was feeling sick.
17 That's Peter, the boy _____ has just arrived at the airport.
18 What did you do with the money _____ your mother gave you?