1.   A flood of refugees could pose a serious problem for neighbouring countries.

2.   Air pollution is our most serious environmental problem.

3.   All this talk of war is just an attempt to draw attention away from the serious economic problems that face our country.

4.   And the fact that both doctors were insured by the same company must have posed a serious problem for the company.

5.   And, then he developed serious problems with his right elbow.

6.   Anomie theorists and their subcultural followers reversed the classical position on these matters, and in doing so encountered serious problems.

7.   Another serious problem for environmentalists is the type of tree and forest planted.

8.   As Hoffman indicated, Macintosh in its nascent form had some serious problems.

9.   As more and more land was planted with cash crops, the lack of pasture became a serious problem in many districts.