479.The telephone ______，but by the time I got indoors, it stopped.
A.had rung
B.was ringing
C.rings
D.has rung
480.What's that noise?
Oh, I forgot to tell you. The new machine _______.
A.was tested
B.will be tested
C.is being tested
D.has been tested
479.答案是B;由句意判断,电话铃在我进入之前一直在响。
480.答案是C;根据上文的问话可以断定机器正在被检测，故选C。
