The main topic of conversation was Tom's new girlfriend.

交谈的主要话题是汤姆的新女友。

The debate veered away from the main topic of discussion.

争论脱离了讨论的主题。

The main topic of conversation was the likely outcome of the election.

谈话的主题是选举可能产生的结果。

What's the main topic today?

今天的主要议题是什么？

These two problems was the main topic in the meeting.

这两个问题在会议上占了首要地位。