When I was there, he was still working. He said that he (1) for the last two hours (2) that he was going to stop (3) . He added that if I had arrived ten minutes later, I (4) at home. When I mentioned that the house looked quite (5) , he said that the woman (6) usually cleaned it had been sick for some time and (7) for over a week. When I asked him (8) he did not do it himself, he said that he (9) to do so if Mrs. Jones did not come the (10) day.

[A] and [B] but [C] so

简述闪烁探测器的工作原理。