The loser has to offer his body to science by participating at a hard and tough challenge.

"Getting town approval is the hardest challenge," he said.

Then, through a series of increasingly harder challenges, he (and the reader) begin to understand the principles in question.

Day 2 - The four recruits undertake harder challenges as they try to progress.

"He might be the hardest challenge for me this year."

She had expected that Father would set a hard challenge for her, and she was ready to do his will.

"Talk about a hard challenge right there," Miller said.

As a result, the administration and Republican leaders, who are committed to producing a bill, face an extraordinarily hard challenge.

The winners won great prizes, while the losers were suffering hard challenges.

This is perhaps the hardest challenge in the history of international diplomacy.