This year must have been one of the most challenging yet for the travel industry.

"I have seen the city in its most challenging times," he said.

The last day on the river is also one of the most challenging.

It is certainly the most challenging show we do on the network.

The higher difficulty levels are considered by some players to be the most challenging of any music game.

I'm trying to come back into what I think is the most challenging event right now.

Perhaps most challenging of all, though, is having to balance school and work.

Someone asked what was the most challenging part of making a movie.

King is perhaps the most challenging character to beat the game with.

One of the most challenging shows seen in this country for some time.