问题补充:
Only when permission allowed to enter the lab.
A. a teacher has given; are the students
B. has a teacher given; are the students.
C. has a teacher given; the students are
D. a teacher has given; the students are
答案:
(答案→)A. a teacher has given; are the students
B. has a teacher given; are the students.
C. has a teacher given; the students are
D. a teacher has given; the students are
解析:only 引导的状语从句放句首时,主句要倒装。