The manager of a small building company was very surprised to get a bill for two white mic

e which one of his workmen had bought. He sent for the workman and asked him why he had the bill sent to the company.

"Well," the workman answered, "you remember the house we were repairing in Newbridge last week, don't you？ One of the things we had to do there was to put in some new electric wiring. Well, in one place we had to pass some wires through a pipe thirty feet long and about an inch across, which was built into solid stone and has four big bends in it. None of us could think how to do this until I had a good idea. I went to a shop and' bought two white mice, one of them male and the other female. Then I tied a thread to the body of the male mouse and put him into the pipe at one end, while Bill held the female mouse at the other end and pressed her to help her. I suppose he was a gentleman even though he was only a mouse. Anyway, as he ran through the pipe, he pulled the thread behind him. It was then quite easy for us to tie one end of the thread to the electric wires and pull them through the pipe."

The manager paid the bill for the white mice.

The manager wondered why ________.

A．the workman sent a bill to the company

B．the mice bought for the job were a male and a female

C．the workman had paid for the mice

D．mice were needed in repairing a house