29. ---- I wonder ______
Mr. Black changed his mind to take part in the movement.
---- After he listened to the speech by Mr.
King.
A. when was that it B. when was it that C. when that
was D. when
it was that
30·You can make a complaint to
the local government ______ you are happy with the way things are.
A. unless
B. if
C. once
D. as