题目

   Billiards（台球） is my favorite ball sport. The English player Ronnie O’Sullivan and Chinese player Ding Junhui are   46   my favorite players. They play it very well. I hope I’ll be   47   to play it well, too. Of course, it is only a dream. Of the two players, I  48   O’Sullivan, because he played it so quickly in the races. When I was nine, I   49  this ball sport for the first time. My PE teacher, Mr. Xu, and I became good   50   because of billiards. I still remember that one day Mr. Xu and I played billiards   51   class. We were so excited 下列事实不能说明生态系统自动调节能力具有一定限度的是(　　)A．当草原遭到蝗虫的采集后，草原植物就增强再生能力B．在北极苔原地区，若地衣受到大面积破坏后整个生态系统遭到破坏C．海洋鱼类在适当捕捞的条件下，鱼类产量能保持相对稳定D．受到轻度污染的河流，一段时间后污染消除