阅读短文选择正确答案。
Betty is a little girl. She is only five years old. She doesn't go to school. Of course, she doesn't know how to read or write. But her sister Lucy is a schoolgirl. She is ten. One day, Lucy sees Betty is writing something in the study.
"What are you doing, Betty?" she asks.
"I'm writing a letter to my friend, Amy." says Betty.
"But how can you?" says her sister. "You don't know how to write."
"Well," says Betty. "It doesn't matter, because Amy doesn't know how to read."
B. 
C. 
D. 
E. 