1.   But perhaps the biggest challenge and one that receives little attention is the enormous technical complexity of the Internet.

2.   But the biggest challenge many entrepreneurs face is the temptation to go off-track.

3.   Finding a place to put the tons of snow now sitting on already clogged urban streets is perhaps the biggest challenge.

4.   Happiness, in a way, is the biggest challenge.

5.   His biggest challenge with this unit will be motivation.

6.   However, the biggest challenge we face today is a willingness by some in the entertainment industry to produce whatever sells.

7.   Inventing an economically efficient system for counting and cutting emissions that encompasses the public and private sectors, is the biggest challenge.

8.   This could be the biggest challenge of his career.

9.   McManus is facing the biggest challenge of his career.

10.   Martins now faces the biggest challenge of his career.