BEFORE THEIR VISITORS CAME, THEY ... EVERYTHING.A. HAVE PREPAREDB....

13. - 3500 CAU TRAC NGHIEM ON TAP AV THCS
3500 CAU TRAC NGHIEM ON TAP AV THCS

13. Before their visitors came, they ... everything.

a. have prepared

b. were preparing

c. had prepared

d. had been prepared

 c