Smoking is one of the ______ of heart disease and it kills lots of people every year.

The coin was almost worthless. So it was of small ________.

  —Nowadays the doctors are trying their best to reduce the people’s fear__________ they would be affected by the present disease called “Bird Flu （禽流感）”.

_________ most students, she was always well prepared and never came to class late.

According to news reports, personal _____of guns in the USA causes a lot of trouble.