It worried her a bit _____________ her hair was turning grey. 

Researchers have found clear and convincing evidence ________ happiness isthe key to better health and longer lives.

A story goes ______ Elizabeth I of England liked nothing more than being surrounded by clever and qualified noblemen at court. 

. Rather than _______ on a crowded bus, I always prefer _____ an electric bicycle.

—Would you prefer to attend a private tutor?—I’d rather _____ for a class than _____ a tutor.