11.Five years ago her brother was ____ university student of _____ physics.
A. a; the B. an; the C. an; / D. a; /
12. -----What can I do for you?
------I`d like to exchange this blue shirt ____ a yellow one.
A. to B. with C. for D. of
13. I ______ through that bitter period without your generous help.
A. couldn’t have gone B. didn’t go C. wouldn’t go D. hadn’t gone
14. The two girls are so alike that strangers find ___ difficult to tell one from the other.
A. it B. them C. her D. that
15. —It’s a long time _____ I saw you last.
—Yes, and what a pity it is now that it will be a long time ____ we see each other again.
A. before; since B. since; when C. since; before D. when; before
