"This nuclear testing poses a grave threat, a challenge to the NEPT regime and also poses a grave threat to the peace and security,stability, not only in the Northeast Asian region, but also the whole global community,".

VOA: standard.2009.05.25

Why is testing always a challenge?

测试为什么经常是个挑战呢？好？

麻省理工公开课 - 计算机科学及编程导论课程节选