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

His______behavior. made everyone nervous. He was always rushing to open doors and perform. other small tasks, apologizing unnecessarily for any inconvenience that he might have caused.
A．oblivious
B．observant
C．obsequious
D．obsolescent

__ we have finished the book, we shall start doing some exercises.
A．For now
B．Since that
C．Now that
D．Since already

Careful testing is necessary before any more experiments can continue with the exploring submarine.
A．needful
B．in need of
C．necessity
D．of necessity

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

听力原文：Unless the whole production cost could be reduced to a reasonable limit, the company would have to double its budget by next year.
（25)
A．The company's budget must be reduced reasonably next year.
B．The company's production cost is expected to rise next year.
C．The company has to stabilize its production cost.
D．The company is likely to go bankrupt because of its limited budget.