请高人指教,本人就读网络专升本,

请高人指教,本人就读网络专升本,
46.This company was the first____________portable radios as well as cassette tape recorders in the world.
A.producing
B.to produce
C.having produced
D.produced
满分：2 分
47."I'm sorry to have kept you waiting." "Oh,not at all.I ____________here only a few minutes."
A.have been
B.had been
C.was
D.will
满分：2 分
48."Did you enjoy last night's concert?""Yes.Though the last piece____________rather poorly."
A.was played
B.played
C.was playing
D.playing
满分：2 分
49.We can go when the ground____________.
A.is drying
B.has dried
C.dried
D.dry
满分：2 分
50.A number of paintings in the castle are believed____________in a fire.
A.being destroyed
B.having been destroyed
C.to be destroyed
D.to have been destroyed