阅读下列短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。
A
It was my first fulltime job as a teacher in a high school in Riverside, California, The Department Chair told me that I would teach a class Introduction to Writing, a freshman course. I felt very confident.
It was my first class. When I entered the classroom, I was surprised. Freshmen? These kids looked too tall and mature (成熟的) to be freshmen! I still didn't have a class list of names, so I started by talking with them and asking questions. They took notes and everything was fine until I noticed a tall boy eating a piece of cake. Rule 1, clearly written on the board was “NO FOOD OR DRINK IN CLASS”. I got a little mad and asked him to read the rule out aloud. He did so and he got mad too!
I asked him, “Did you understand what you read？” This made him even madder.
“Yes, I did.”
“Well, then, what were you doing just now？”
We were both getting madder and madder.
“I was eating a piece of cake.”He took another bite (咬) and looked at me angrily.
“Well, get up, go outside and throw the cake away.”
And then both of us made a mistake. He said, “Here, I don't even want it.”Then he handed it to me. He put the piece of cake on my hand. The icing of the cake went between my fingers, making a real mess. He was very tall, but he was sitting in a chair and I was standing next to him, mad and angry. I hit the cake on his hair!
The class started laughing and clapping. Somebody got up, went to the board and wrote “Teacher — 1; Mark — 0”. I didn't know whether I was supposed to laugh or not, but I couldn't help it. And then, Mark got up and left.
The story was all over the school by the next period. Some students came to me and said, “I heard that terrible things will happen if somebody tries to eat cake in your class！” Oh, how embarrassing!
Now I still teach, but I'm much better at dealing with students.
21．What did the author mean by saying “I couldn't help it” in the lastbuttwo paragraph?
A．She became angry.
B．She started laughing.
C．She started crying.
D．She couldn't help the student.
22．What did the author most probably realize after that experience?
A．Students can eat cake in class.
B．Her students were really kind to her.
C．She wasn't good at teaching freshmen.
D．She should do better in dealing with students.
23．What might be the best title of the passage?
A．My Embarrassing Experience of Being a Teacher
B．Sharing a Piece of Cake with My Student
C．It's Important to Have Class Rules
D．How to Control Your Emotion
