EPA adds challenges on the site and the public can post solutions to these challenges.

This ultimate contest will upstage Hawaii's world championship by adding intellectual and artistic challenges to the grueling physical tests.

Ironically, the flat-slab structural system that was so innovative in the 1950s now limits ceiling height to 9 feet and adds challenges to any renovation.

He started with the old tote roads that were already in place, then added extra challenges.

The skills and attitudes needed to manage polyamorous relationships add challenges that are not often found in the traditional "dating-and-marriage" model of long-term relationships.

Some said that globalization added challenges to the city's future as a cultural hub.

Some games add special challenges such as combat and slaloms.

The rise of Cloud computing has also added challenges to the collection of evidence.

Added unlockable game challenges, which adds challenges by reaching predetermined goals in specific games.

This stage would obviously add serious diplomatic challenges to an already complicated scientific protocol.