My teenage son Karl became withdrawn after his father died. As a single parent, I tried to do my best to talk to him, but the more I tried, the more he pulled away. When his report card （成绩报告单）arrived during his junior year, it said that he had been absent 95 times from classes and had six failing grades for the year. At this rate he would never graduate. I sent him to the school adviser, and I even begged him. Nothing worked.
One night I felt so powerless that I got down on my knees and pleaded for help. “Please God, I can’t do anything more for my son. I’m at the end of my rope. I'm giving the whole thing up to you.” Just then, I got a phone call. A man introduced himself as the headmaster, “I want to talk to you about Karl’s absences.” Before he could say another word, all my disappointment and sadness over Karl came pouring out into the ears of this stranger. “I love my son but I just don’t know what to do. I’ve tried everything to get Karl to go back to school and nothing has worked. It’s out of my hands.” For a moment there was silence on the other end of the line. The headmaster seriously said, “Thank you for your time” and hung up.
Karl’s next report card showed a great improvement in his grades. Finally, he even made the honor roll（光荣榜）. In his fourth year, I attended a parent-teacher meeting with Karl. I noticed that his teachers were astonished at the way he had turned himself around. On our way home，he said, “Mum，remember that call from the headmaster last year?” I nodded. “That was me. I thought I’d play a joke but when I heard what you said, it really hit me how much I was hurting you. That’s when I knew I had to make you proud.”
By saying “Karl became withdrawn” the author means that the boy changed entirely and ________.

A．he preferred to stay at school

B．he stayed at home all day

C．he refused to talk to his mother

D．he began to like his life

There was silence on the other end of the line because ________.

A．the speaker was too moved to say anything to his mother

B．the speaker waited for the mother to finish speaking

C．the speaker didn't want the mother to recognize his voice

D．the speaker didn’t want to interrupt the mother

What is the main idea of this passage?

A．Children in single-parent families often have mental problems.

B．Mother’s love plays an important role in teenagers’ life.

C．Being understood by parents is not necessary to teenagers.

D．School education is a failure.

Which is not true according to the article?

A．Karl changed a lot after his father died.

B．What Karl did at school showed that he didn’t love his mother.

C．Karl’s mother tried many ways to help him.

D．Karl’s teachers were surprised at his change.