It is useless to speculate why he did it.

对他为什么这么做妄加猜测毫无用处。

《牛津词典》

It's always hard to speculate about the future.

推测未来总是很难的。

《柯林斯英汉双解大词典》

It's tempting to speculate about what might have happened.

大家不禁猜测，到底发生了什么事。

《牛津词典》

Clinton,appearing at the State Department's daily press briefing, said she did not want to speculate on Iran's political future, but she that the reported recount is unlikely to do much to defuse election-related tensions.

VOA: standard.2009.06.29

Those are easy. There's no getting around reading those things, and then it gets to be more interesting as we speculate.

这些都是显而易见的,还有些历史是,没有记录的,靠的是人们丰富的联想

耶鲁公开课 - 古希腊历史简介课程节选

"Therefore, we don't want to speculate on either the project or project feasibility, " a spokesperson said.

CNN: Can plan to fly Concorde again get off the ground?

The resulting turmoil in commodity markets led a number of hedge funds to speculate widely.

FORBES: Magazine Article

Asked if they were being readied for release, Vujovic said he did not want to speculate.

CNN: NATO strikes target Serb ground forces, complicate GI release efforts