To keep healthy, most retired old people _____ jogging as a regular form of exercise．

The sign _____ “In case of _____ fire, push _____ red button.” [ ]

Ten thousand dollars _____quite a large sum.

The singer felt very sorry and decided he would never drive again after drinking. The traffic accident was really a _________ to him.

Why can your neighbor know so much about London?—He ____ have been there before.