1.   And it underscores the challenges faced by scientists and parks officials as they try to preserve intricate ecosystems.

2.   Blair underscored the challenge facing the politicians and the people of Northern Ireland.

3.   Aerospace industry officials say the crash underscores the challenge facing modern aviation, to reduce the number of crashes even as the number of flights increases.

4.   But the numbers also underscore the challenge that remains.

5.   But they also underscore the challenge of keeping fans who are an ocean apart from actual sweating, dunking teams from spending their sports money elsewhere.

6.   But they also underscore the challenge of keeping fans who are an ocean apart from spending their sports money elsewhere.

7.   He told the Texas Higher Education Coordinating Board Thursdaythat the new data underscore the challenge in ensuring Texas has an adequately trained work force in the coming years.

8.   Nighthawk also underscores the challenge to keep the border safe with limited resources in a rugged, remote part of the world.

9.   The battle also has underscored the challenge posed by harsh environments, chosen not by the United States but by the Al Qaeda and Taliban militants.

10.   The bloodshed underscored the challenge facing retired Marine Corps Gen. Anthony Zinni and Assistant Secretary of State William Burns as they try to push both sides toward a truce.