A、The speaker’s friend entered his house from back door. B、The speaker’s friend entered his neighbor’s house by mistake. C、A thi

An old friend from "abroad, whom I was expecting to  stay with me, telephoned from the airport to tell me that he had arrived. I was still at the office at the time, but I had  made arrangements for his arrival. After explaining where  my new flat was, I told him that I had (28)left the key under a stone near the door. As I was likely to be at home  rather late, (27)I advised him to go into the kitchen and  help himself to food and drink.
    Two hours later, my friend telephoned me from the  flat. At the moment, he said, he was listening to some of my records after having just had a truly wonderful meal. He had found a pan on the gas stove and fried two eggs and had helped himself to some cold chicken from the refrigerator.  Now he said, he was drinking a glass of orange juice and he  hoped I would join him. I asked him if he had reached the flat without difficulty, he answered that he had not been able to find the key under the stone, but fortunately the living- room window just by the apple tree had been open and he  had climbed in. (26)I listened to all this in astonishment. There is no apple tree in front of" my living-room, but there is one in front of my neighbor’s.