11、
A．efficient
B．interesting
C．effective
D．impressive


12、
A．if
B．whether
C．however
D．whatever


13、
A．information
B．documents
C．files
D．messages


14、
A．let
B．make
C．allow
D．letting


15、
A．what
B．why
C．when
D．how


16、
A．introducing
B．inviting
C．investing
D．interrupting


17、
A．partly
B．mostly
C．lastly
D．completely


18、
A．favor
B．rule
C．information
D．permission


19、
A．above
B．under
C．below
D．at


20、
A．no matter
B．even if
C．unless
D．also