Even before the laws of quantum mechanics were fully developed, the phenomenon of radioactivity posed a challenge to determinism.

In fact, the dot-com phenomenon posed exactly this kind of challenge to many traditional ways of thinking about business.

Thunderstorms, and the phenomena that occur along with them, pose great hazards to populations and landscapes.

But for everyone in a blended family, the phenomenon that has become known as the December Dilemma poses a particular logistical challenge this year.

This suburban phenomenon posed a political challenge to President Bush from the very beginning.

Even so, the phenomenon of wealthy candidates like Mayor Michael R. Bloomberg has posed new challenges for the board and its mission.

Smith believed "there was only one chance in 10,000 that the phenomenon posed a threat to the security of the country, but even that chance could not be taken."

But the strolling phenomenon poses an acute problem for a government already intensely focussed on how to prevent the wave of unrest from spreading to China.

He contends the phenomenon poses enough mysteries about the human brain to warrant scientific investigation.

The phenomenon could pose a hazard for astronauts on long-term missions.