Question

read the passage. jonas salk and polio polio is a viral disease that produces flu - like symptoms and may occasionally cause muscle weakness or paralysis. throughout the first half of the twentieth century, the disease was common, and parents feared that their children would lose the ability to move their arms or legs. in 1947, dr. jonas salk began studying polio at the university of pittsburgh in search of an answer. he discovered three basic types of polio viruses and began to develop a vaccine that would protect against all three. testing began in 1952, with vaccinations eventually given to about two million children. the vaccine was shown to be effective and was put into general use in 1955. jonas salk became a hero and received an award from president dwight d. eisenhower. what is the main, or central, idea of the passage? jonas salk discovered that there were three different viruses that caused the disease called polio. jonas salk developed a vaccine that provided protection against the feared disease polio. jonas salks vaccine for polio was tested in the early 1950s and put into general use in 1955.

Explanation:

The passage starts by introducing polio as a feared disease. Then it focuses on Jonas Salk's work: he discovered polio virus types, developed a vaccine, tested it (with large - scale vaccination of children), and the vaccine was proven effective and put into general use. The first option only mentions the discovery of virus types, which is just a part of his work. The third option only focuses on the testing and general use, which is also a part. The second option encompasses the whole process of his work (discovering viruses, developing the vaccine, and the vaccine providing protection against polio), which is the main idea.

Answer:

Jonas Salk developed a vaccine that provided protection against the feared disease polio.