One evening I went out and left my 17-year-old son in charge of his 8-year-old brother and 4-year-old sister. On this occasion, the work was made less troublesome by the presence of his girlfriend. I left with complete confidence that the older children would do a wonderful job of babysitting the younger children and the younger children would do a wonderful job of accompanying the older ones. Later, I discovered that complete confidence was the last thing I should have left home with.
I had decided to return home earlier than planned so that my son and his girlfriend could go out. I called home with this happy news. But instead of hearing his cheerful, grateful voice on the other end of the line, all I heard was the sound of a telephone ringing.
It was, I should point out, after 10 p.m., when the two younger children should have been in bed, and when the two older children should have been answering the phone. “I’ll give him a lesson,” I said. I decided they must be outside. Why they might be outside at 10:30 on a wintry night I had no idea, but it was the only explanation I could come up with.
Finally, in desperation, I called his girlfriend’s house. After what seemed like countless rings, his girlfriend answered. “Yes,” she said brightly, “He’s right here.”
He came on the phone. I was not my usual calm, rational(理智的) self. After all, one of the rules of survival for modern parents is that you can’t trust modern teenagers. “Where are the children?” I said. He said they were with him. They had done nothing wrong. My son had taken the younger children over to his girlfriend’s house just for ice cream and cake. This was too good to be believed. Well, it turns out that I shouldn’t have believed it. It was only part of the truth.
The following Saturday evening we were at my parents’ home, celebrating my birthday. My oldest son gave me the children’s gifts. Mounted and framed were a series of lovely color photographs of my children, dressed in their best clothes, and wearing their most wonderful expressions. They are pictures to treasure a lifetime, all taken by the father of my son’s girlfriend.
51.The author went out and left her eldest son in charge of the younger children because ______.

A．she knew that his girlfriend was a good baby-sitter

B．she believed he could take good care of the younger ones with the help of his girlfriend

C．the older children have always loved the younger ones

D．she could not find a baby-sitter on that winter night

52.Shortly after the author left home one evening, she discovered that ______.

A．she shouldn’t have completely trusted her son

B．her son had left home with his girlfriend

C．her son had brought his girlfriend home

D．she should have taken the children along with her

53.The sentence “It was only part of the truth.” (Para. 5) implies that the children not only enjoyed ice-cream but also ______.

A．had their pictures taken	B．had a birthday party
C．framed some photographs	D．showed off their best clothes

54.Which of the following possible titles best expresses the main idea of this passage?

A．An Evening Out	B．Modern Teenagers
C．A Precious Birthday Gift	D．Mother and Children