Final answer:
Mandarin is the most used language from the Sino-Tibetan language group, spoken by nearly a billion people worldwide, making it the language with the highest number of native speakers among the Sino-Tibetan languages.
Step-by-step explanation:
The most used language in the world from the Sino-Tibetan language group is a) Mandarin. Mandarin Chinese is spoken by approximately 70 percent of the Chinese population, making it not only the most spoken language within China but also the language with the highest number of native speakers globally, with nearly a billion people speaking it as their primary language. As part of the Sinitic branch of the Sino-Tibetan language family, Mandarin is one of several dialects of Chinese, which differs significantly from others such as Cantonese, spoken in Southern China. Mandarin has become the dominant language and is used for government, business, and education in China. The writing system, which is character-based, requires literacy in thousands of logograms, a challenge shared by Mandarin and other East Asian languages that have adapted these characters.