A.
B.
C.
D.

A.Was built
B.Building
C.To have built
D.Built

A.beneficial
B.costly
C.valuable
D.worthy

A.would have joined
B.will join
C.had joined
D.would join

A.collect
B.gather
C.achieve
D.master

A.about
B.on
C.for
D.at

A.was playing
B.had played
C.played
D.is playing

A.result in
B.hold on
C.take over
D.keep to

A.is he
B.does he
C.isn't he
D.doesn't he

A.knowledgeably
B.knowledgeable
C.knowledge
D.know