11.   Not surprisingly, dead metaphors as a rule present fewer problems to foreign learners of a language than idioms do.

12.   Technical problems To the naked eye the brain has a disturbingly homogeneous appearance.

13.   The procedures cover each stage from initial reporting of a problem through to eventual correction.

14.   The space agency linked the problem to repairs made earlier that required the nozzles to be removed and replaced.

15.   These mountain roads present problems even to experienced drivers.

16.   They also needed to stop rationalizing the problem to themselves and bending over backwards to be fair.

17.   They pose problems to foreign language learners and native speaker learners alike.

18.   Large classes present great problems to many teachers.