What we know about certain diseases are still not sufficient to prevent them from spreading easily among the population.

Society uses such human emotions as proud, shame, guilt, and fear to maintain itself.

Regarding as one of the leading figures in the development of the short story, O Henry is the author of many well- known American novels.

A novel is a story long enough to fill a complete book, in that the characters and events are usually imaginary.

I enjoyed talking to the people with that I met at the party last night.

Developing new technologies are time-consuming and expensive.

It is vitally important that she takes this medication night and morning.

Had it not been for you help me, I wouldn't have succeeded.