Scientists also have no idea how long it will be before all wild animals in the cages _____. 
#99827
A
should be set free
B
will be set free
C
are set free
D
would be set free
推荐题目
When Nancy was at college, she ______ three foreign languages. But I am surprised to find that she ______ all except a few words of each.
#101433
A
spoke; had forgotten
B
had spoken; had forgotten
C
spoke; has forgotten
D
had spoken; has forgotten
Instead of telling the joke he _______, Crystal made up a new one.
#102101
A
made
B
has made
C
had made
D
would make
By the time Jack returned home from England, his son  _______  from college.
#100009
A
graduated
B
has graduated
C
had been graduating
D
had graduated