C

    My family lives in London. In the morning, my father goes to work and we go to school. My father takes us to school every day. My mother stays at home. She does the housework. She always has lunch at home, and visits her friends in the afternoon. In the afternoon, we go home from school by bus. My father gets home from work late. At night my two brothers and I always do our homework. We go to bed at about ten. My father and my mother usually read newspapers. We can watch TV at the weekend.

在下列表达式中，不能表示代数式“6a”意义的是（　　）