It was a very happy family. They were fairly well-off. The father, Leopold, was a master o

f music in Austria. His mother was warm-hearted. There were two children, Marianne, a schoolgirl, and little Wolfgang, a child not quite four years old. Marianne was learning to play the piano, and day after day Leopold stood behind her as she practiced. How patient their father was, and how cleverly he showed Marianne how to play some particularly difficult pieces! She was making progress, very good progress, and that was excellent. And there, almost lost in the big chair, sat Wolfgang, who never had to be told to keep quiet when looking over Marianne's shoulder. At that moment Wolfgang climbed on his father's knees and begged to be allowed to play the pretty piece Marianne had now mastered. What a joke that was! Picking up his baby son, Leopold laughed and said, "Look at your hands. You must wait, little man!"

There was no end to the fun during tea, and Marianne had to tell her mother about Wolfgang wanting to play a difficult piece. When the meal was finished, Marianne helped to clear away the dishes. Suddenly Leopold got up. "Listen!" said he in a surprised voice. "Listen! Marianne is playing the piece better than ever!"

But Marianne was washing dishes in the kitchen.

His wife following, Leopold walked quietly upstairs, the lamp in one hand, his music book in the other. He pushed open the door, and there was little Wolfgang playing in the darkness. "I love it" whispered the child.

It was the beginning of Mozart's life of music.

Wolfgang was quiet when his sister practiced the piano because______.

A．he loved music

B．he liked his sister

C．he didn't want to make a noise

D．he didn't feel well