11.   His reasons remain hidden in the confidential memo.

12.   One reason there remains broad support for environmental measures here is that people can see enormous improvements in their lifetime.

13.   Reasons for caution remained, however.

14.   The reasons remain uncertain, but some cases may be associated with other carcinogens.

15.   The reason for this remains unknown.

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

17.   The reasons remain unclear.

18.   Their reasons for backtracking remain unclear, but most experts say they probably see greater advantage in staying clear of an unpopular government and an increasingly unpopular president.

19.   There remains every reason to worry about his policies and plans, despite his promises on Monday to repair relations with his opponents.

20.   Though many researchers agree that several species of these migrant songbirds are decreasing, the reasons remain controversial.