A、His telephone went out of order. B、The buyers had to leave soon. C、He began to work at 8 a.m. D、He had made an appointment wit

When my husband was promoted, we put our house up for sale. Three weeks later, it was still on the market. I became a busy housekeeper. Every room had to be kept tidy, and dishes had to be washed and put away when used. Then one day the doorbell rang unexpectedly at 8 a.m. Sleepily, I opened the door and saw our agent standing there with a couple from New York. "There had been no time to call," he explained, "[20]because the couple had to catch a plane home."
    The three people made their way past the dirty breakfast dishes on the kitchen table and into a bedroom with unmade beds. As I retreated into a bathroom to comb my hair, I heard the man say something to his wife. Then they both laughed.
    Two days later, the agent phoned to tell me that the couple had bought the house. He repeated what the buyer had said when he handed over the check the following day: "That house has a warm, lived-in feeling, just like ours."
19. Why did the speaker sell her house?
20. Why did the agent call on the speaker so early in the morning?
21. Why did the couple laugh in the speaker’s house?