Which one of these is not one of the four main purposes? A. To entertain

B. To categorize

C. To express an opinion

D. To persuade

Which is the most engaging way of describing how to prevent eyestrain? o a. the medical term for eyestrain is asthenopia, and is caused by the contraction of the ciliary muscle. o b. to prevent eyestrain, people should not look at screens for as long as they often do. o c. the human eye tires after staring at close objects, such as computer monitors, for too long. o d. remember the 20/20/20 rule: every 20 minutes, look at something 20 feet away for 20 seconds