单项选择题

Young horses may develop a______ cough before and during exercise, particularly when cold air is breathed in during warming-up exercise or under dusty conditions.

A．perpetual
B．permanent
C．chronic
D．sustained
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单项选择题
Successive committees have______ over this problem without finding a solution.
A．reckon
B．ponder
C．speculate
D．presume
单项选择题
The man in black is suspected to be a shrewd spy behind the mask of an automobile business- man and the police therefore begin to______ his every move.
A．mobilize
B．warrant
C．manipulate
D．supervise
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