The major part of Central Asia is dominated by language families falling under the Altaic category. Here`s why:

Option 1: Indo-European - This is primarily spoken in Europe and parts of South Asia, not Central Asia.

Option 2: Sino-Tibetan - Though a major language family, it`s mainly spoken in East Asia and some regions of Southeast Asia, not Central Asia.

Option 3: Austric - This language family includes languages mainly spoken in Southeast Asia and parts of East India, again not dominant in Central Asia.

Option 4: Altaic - This language family encompasses several language groups including Turkic, Mongolic, and Tungusic, prominently spoken in Central Asia, thus marking the correct answer.

Altaic languages are found in a broad area stretching from Turkey to Northeast Asia, making it the `dominant` language family in Central Asia.