She was nominated to speak on our behalf.

她被指派代表我们发言。

She was billed to speak on 'China—Yesterday and Today'.

据宣传她要发表题为“中国—昨天和今天”的演讲。

If you're a person who uses pet phrases when you speak, you should train yourself carefully not to use these when you speak on the phone.

如果你是一个平常说话喜欢带口头禅的人，你就要训练自己小心地避免在接听电话时使用这些。

They are best qualified to speak on this question.

他们对这个问题最有发言权。

I heard him speak on HIV and I invited him here.

我听他谈论艾滋病毒问题并邀请他来此。