21. Sarah，hurry up，I’m afraid you don’t have time to__________.
A. get change B. get changing
C. get to change D. get changed
22. You can’t have this football back _________you promise not to kick at my cat again.
A. because B. until C. when D. since
23. The first two services are free，______the third costs￡35.
A. while B. whether C. what D. which
