discussion可数吗?

　　The discussion focused on three main problems.

　　讨论集中在三个主要问题上。

　　I tried to lead the discussion back to the main issue.

　　我试图把讨论引回到主要问题上。

　　There was discussion about the fire and its likely cause.

　　对那场火灾及其可能的.起因进行了讨论。

　　They finally settled down to a discussion of the main issues.

　　他们终于开始讨论一些主要问题了。

　　The article served as a useful starting point for our discussion.

　　这篇文章成了我们展开讨论的良好起点。