根据短文理解，从A、B、C、D四个选项中选择最佳答案填空。

    It was a Monday morning. When a teacher walked into the  1  , he heard a low voice: “Here is the teacher. I am 2this boring. fellow(烦人的家伙) is going to talk about putting in commas(逗号).” It was  3  voice. His name was Bill. He was talking  4 the boy next to him.

The teacher didn't get angry. He said 5 about it. He really began to talk about putting in commas, and then he wrote 6 the sentence. “Bill says the teacher is a boring fellow.''

The class 7 and Bill's face 8 red.

“Now,” said the teacher, “I'll 9 you how important commas are.''

He put two commas in the sentence, and now read, “ 10 is a boring fellow.''