IF SOMEONE KNOCKS __________ THE DOOR _____________ NIGHT, DON'T O...
12. If someone knocks __________ the door _____________ night, don't open it.
a. at / at
b. on / at
c. up / in
d. at / on
12. If someone knocks __________ the door _____________ night, don't open it.
a. at / at
b. on / at
c. up / in
d. at / on