Department of Homeland Security Secretary Janet Napolitano says one of the biggest challenges is finding the right people to handle the job.

VOA: standard.2009.08.11

One of the biggest challenges to date has been related to cultural relativism.

在那之后的诸多挑战中,最值得一提的就是，“文化相对主义“

普林斯顿公开课 - 人性课程节选

One of the biggest challenges is traffic. In some areas there are marked bike lanes;

VOA: standard.2010.07.30

But the critics and supporters agree one of the British national health service's biggest challenges, as it enters its seventh decade, are the mounting cost of new technology and medicines, and an aging population.

VOA: standard.2009.09.24