what computer game can you play

6.games
7.Does; do
8.Don't swim
9.open
10.isn't

肯定加啊，应该是He plays computer games on the weekend.
否则还有一种可能就是原句是疑问句：Does he play computer games on the weekend?
这样句子前有一个助动词Does,后面的动词就全是原型
总之绝对没有楼主说的He play computer games on the weekend.这个句子

因为电脑游戏并不是只有一个，所以要用game的复数的形式也就是games。