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
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
A
only 引导的状语从句放句首时，主句要倒装。