单项选择题

We shouldn't expect a technical innovation can be made perfect overnight. It has to be improved ______ in fact.

A．from cover to Cover
B．at a good pace
C．in succession
D．step by step
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单项选择题
Children begin to communicate by making noises ______ they are able to speak a language.
A．before long
B．long before
C．long ago
D．long after
单项选择题
There ______ nothing to discuss further, the chairman got to his feet, then left the meeting room.
A．leaving
B．having
C．being
D．is
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