Worse: Three factors affectthe rate of a reaction: concentration, surface area, and temperature.
Right: The rate of a reaction is affected bythree factors: concentration, surface area, and
temperature.
(4)
冒号后可以加入一个主句，用以解释冒号前的内容。
EG: On January 1, 2000, the national mood wascompletely different from what it would become just a few years later: at theturn of the century, given a seemingly unstoppable stock market and a seeminglypeaceful world, the country was content.
