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 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

"President Obama embodies the new spirit of dialogue and engagement on the world's biggest problems: climate change, nuclear disarmament and a wide range of peace and security challenges,".

VOA: standard.2009.10.09