單項(xiàng)選擇題The ratio of the work done by the machine()the work done on it is called the efficiency of the machine.

A.against
B.with
C.to
D.for


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1.單項(xiàng)選擇題His inability to learn foreign languages was a(n()to his career.

A.objection
B.defect
C.obstacle
D.depression

3.單項(xiàng)選擇題When you go to the doctor he asks you to describe your()so that he can make a diagnosis (診斷).

A.indications
B.signs
C.symbols
D.symptoms

4.單項(xiàng)選擇題He ran so fast that he was out of()

A.air
B.oxygen
C.breath
D.wind

5.單項(xiàng)選擇題Be careful with those fireworks; they are()to go off unexpectedly.

A.easy
B.probable
C.available
D.liable