阅读理解。
It was graduation day at the university where I work and a beautiful day quite unlike the first graduation I attended as a young professor. On that cold day years ago, as we watched the students walking into the hall, one of my colleagues turned to me and said, "Graduation will be one of the happiest and one of the saddest time of your life." At my inquiry, he answered, "Because the students you have gotten to know have to leave." As years went by, my previous confusion about my colleague's words no longer existed. When I came across naughty students, I have had to rethink why I chose to be a teacher. It obviously isn't the money. Once a former computer science student of mine called me, asking me if I wanted to have a change. He was working at Nintendo Corporation. His salary was higher than my current one, though I have more education and have worked for over a decade. With my programming skills, he said he could get me hired I thanked him, but declined his kind offer. A few days before this current graduation, while working on final grades, I found a note a student had slipped in with her homework. She thanked me for being her teacher and said the things she had learned in my class-not about math, but about life-would be things she would remember long after the math skills had faded away. As I finished reading, I remembered why I had become a teacher. Now, on this sunny graduation day, as I again observed the sea of blue hats and gowns, I did so with renewed dedication （奉献) and a deeper sense of satisfaction-I will always be grateful that I am a teacher.
Hearing his colleague's description of graduation for the first time, the author _____.[ ]
A. quite agreed with his colleague B. thought it very funny C. was very puzzled D. was very sad
The computer science student called up the author because he _____.[ ]
A. wanted to inform the author of his present job B. tried to persuade the author to work with him C. wanted the author to share his joy and satisfaction D. thought the author wasn't fit to be a teacher
The underlined part blue hats and gowns refers to _____.[ ]
A. university colleagues B. life memories C. graduates' clothes D. decorations in the hall
The author wrote this passage to _____.[ ]
A. express his devotion to being a teacher B. compare two different graduation ceremonies C. talk about the meaning of graduation D. give advice on how to be a good teacher
The reason why he earns less than the computer science student is that _____.[ ]
A. he was only a young professor B. he didn't do well in his work C. he taught his students more about life than math D. salaries for different careers are different