Answer:
A.
Research is essential to find out which treatments work better for patients. ... Research can find answers to things that are unknown, filling gaps in knowledge and changing the way that healthcare professionals work. Some of the common aims for conducting research studies are to: Diagnose diseases and health problems
About half the world's population (some 3 billion people) speak a language that belongs to the Indo-European language family. The total number of languages and dialects in this family is estimated to be about 439. They include <span>most of the major </span>languages<span> of </span>Europe<span> and western </span>Asia.
English is one of those languages and it is spoken by an estimated 1.5 billion<span> people -- one-fifth of the world's entire population. However, most people who speak English have learned it as a second language. About </span>360 million people speak it as their first language<span>.</span>