阅读短文，下列问题

（C）

    I like sports. I have ten tennis balls, seven basketballs, four volleyballs and five soccer balls. I play tennis with my friends every day.

    I have five baseballs, five volleyballs, two soccer balls. I like ping-pong. It's easy for me. I often play ping-pong with my classmates. I also(也) have three ping-pong bats and some ping-pong balls.

    I don't have any(任何的) balls. I love sports, but I don't play them. I only watch them on TV.

—       you ever       Dali? 

—Never. But I am going there this vacation.

下列哪项不参与生物膜系统的组成（）