皮带机启动失灵可能是由于（）造成的。
参考答案：开关接触不良
I spent five hours repairing the car. The work was ____ simple.
A．nothing but
B．anything but
C．something of
D．all except
Please _____ the numbers and I'm sure they will _____ more than 1, 000. [ ]
A. add up; add to
B. add up; add up
C. add up; add up to
D. add to; add up
