But the challenge of rebuilding Lower Manhattan creates an opportunity to redress the situation.

The challenge was creating a context in which this is accepted by the viewer as part of the show.

The challenge is creating awareness and building your brand.

The bigger challenge, he said, is creating security systems in the real world that are not vulnerable to hackers.

Another challenge was creating the Thestrals, dark creatures that can only be seen by those who've seen death.

His biggest challenge, though, has been creating or adapting dances for about 12 of the hours.

On the other hand, too little challenge creates boredom.

Mr. Singh said his challenge was "to create a pleasant office that converts to something very different, a camera."

Such challenges may create barriers not only to return but to subsistence.

"The challenge for educators and companies is creating a vibrant community around the information," he added.