Over the past few decades,however, scientists have determined that even trace amounts of lead in children's bodies leads to long-term neurological and behavioral problems.

VOA: standard.2009.12.19

Now the trace you notice on the left side has very few and very sharp deflections.

现在大家注意到左侧的变位,很少但是很剧烈。

斯坦福公开课 - 7个颠覆你思想的演讲课程节选

And as you'll see by your handout, I've attempted tend to trace it.

你们可以看看课堂材料，我尝试着去找，了找它的起源，我能找到。

麻省理工公开课 - 计算机科学及编程导论课程节选

"When the gas comes off the digester, it has not only methane in it it also has carbon dioxide And it has a trace of hydrogen sulfide."

VOA: standard.2010.02.23

We are also put in mind of how the war is, in fact, anything but a revel, though it, too, may have been provoked by a cause as insignificant and hard to trace as "some wizard vermin."

我们同样也思考事实上战争，只是一场狂欢，尽管它有可能,是由一个毫不重要难以追踪的“一些害虫“引起的“

耶鲁公开课 - 现代诗歌课程节选

At the same hearing, he says in one of the best studies used molecular fingerprinting to follow an outbreak of drug-resistant bacteria: "You actually can trace the specific bacteria around and they find that the resistant strains in humans match the resistant strains in the animals."

VOA: standard.2010.07.21