单项选择题

For all its extremes, Venus is a(n) incalculable laboratory for researchers studying the weather and climate of earth.

A．invaluable
B．valuable
C．value
D．valueless
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单项选择题
Is there any occasion for my appearance before the court
A．objection
B．cause
C．doubt
D．question
单项选择题
Because this area has a high rate of crime and unemployment, there are only people moving out.
A．incentive
B．incident
C．incidence
D．initiative
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