The punishment had especially taken a mental toll on Robert, who has yet to win a single challenge himself.

His single biggest challenge will be to break the power of the Shiite party militias operating inside and outside the official security forces.

The single biggest challenge for us at Bloomberg is learning to be prepared.

In the days since that time, he had only faced a single challenge to his command.

"The single biggest challenge is to convince the audience that the hero might die."

This is the first time two designers won a single challenge yet were not a team.

This search was the single most important challenge facing Bolivian politicians into the 1980s.

As an industry, this is the single biggest challenge now.

"If the amount changes every year, that is the single most difficult challenge I face as a state college president."

The state, he said, "has met the greatest single fiscal challenge of its 200 years."