单项选择题

A considerable amount of time and money has been invested in ______ this system.

A．defining
B．implying
C．reducing
D．perfecting
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单项选择题
The negotiations which ______ the signing of the treaty took place over a number of years.
A．preceded
B．prescribed
C．proceeded
D．processed
单项选择题
I arrive at nine o'clock, teach until twelve thirty and then have a meal; that is my morning ______.
A．habit
B．custom
C．practice
D．routine
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