__________at the door before you enter the office，or you’ll be considered impolite
#65893
A
Knocking
B
Knocked
C
Knock
D
To knock
推荐题目
The smoggy weather has made us realize terrible problems we are laced with．
#66025
A
how
B
what
C
that
D
which
_______, or he’ll be more angry.
#66258
A
To tell you the truth
B
Telling him the truth
C
Told the truth
D
Tell him the truth
＿＿＿these ancient buildings in this city are!
#66274
A
What perfectly protected
B
How perfect protected
C
How perfectly protected
D
What perfect protected
-- Leo, ________ in bed. --. Sorry, Mom.
#59376
A
can’t sleep
B
not sleep
C
doesn’t sleep
D
don’t sleep