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66、The researchers of the project have to be very careful with every part if it__________ a success.
A．is to be
B．is
C．will be
D．would be

67、__________, Bob still went on with the experiment.
A．As he was tired
B．As was he tired
C．Tired as he was
D．As tired as he

68、The response to the concerts was not warm enough so I decided to postpone booking tickets__________later in the year.
A．until
B．by
C．except
D．beyond

69、He asked a second time, but I couldn't remember__________any of these works.
A．read
B．to read
C．to have read
D．having read

70、The teacher__________, they went on with their discussion.
A．leaving
B．bring left
C．was leaving
D．having left

71、Manyco　mpanies in smaller cities are offering such great professional opportunities that some graduates have a hard time__________them down.
A．turning
B．to turn
C．turn
D．turned

72、Not until the mid-1950s __________most automakers begin offering seat-belts as optional safety features.
A．did
B．had
C．do
D．would

73、Contact the police and tell them all__________you know about the accident.
A．this
B．that
C．what
D．which

74、In the fall the cattle__________from the high country back down to the farm.
A．is driven
B．are driven
C．drives
D．drive

75、After a long walk, we finally found a shelter__________for the night.
A．to stay
B．staying
C．to stay in
D．staying in