一辆运用重车在运送途中进行装卸时、按（）计算作业次数。
A、1次
B、2次
C、多次
D、不计算
参考答案：C
In the advanced course students must take performance tests at monthly______.
A．gaps
B．intervals
C．length
D．distance
The old man has__ __ useful horse and horse can do a lot of things for him.
A．an; a
B．the; a
C．an; the
D．a; the
