11.  No one is sure the exact reason why there are more suicides in the spring, Meyer said, but there are several theories.

12.  NCI officials expect to spend the next month teasing out the exact reasons behind the overall decline in deaths, Larry Kessler, an NCI statistician, said Thursday.

13.  Something about the Masters brings out the best in Olazabal, but even he cannot figure out the exact reason.

14.  The exact reason for the movement is unknown, Glassberg said.

15.  The exact reason for the rise in complaints is unclear.

16.  The exact reasons for the breakup between Lipinski and her coach, Richard Callaghan, remain unclear.

17.  The exact reason for this is not clear, but may result from fat dripping onto the coals.

18.  The spoilers or stabilizers were the most plausible culprits, but the exact reason would remain a mystery.

19.  The researchers were unable to determine the exact reason for the discrimination.

20.  He did not give an exact reason, although he said he had been battling ill health and depression for years.