不可数
All this must happen with very great speed,and only those who 【have had a lot of practice 】at table tennis can do this successfully.
所有这一切的反应都要非常迅速,只有那些打乒乓训练有素的人,才能成功地做到.但是好像有“做操'的意思，是吗？能给出一个例句吗？谢谢没有。我给了例句呀？！