Temperature and density increases from the crust to the core.
The answer is B. In South Asia, Islam found a place in a long-established civilization as invasions by Turkic-speaking warrior groups from Central Asia, recently converted to Islam, brought the faith to northern India. Thus the Turks became the third major carrier of Islam, after the Arabs and Persians, as their conquests initiated an enduring encounter between Islam and a Hindu-based Indian civilization.
Hello There! ^_^
Your question: What were the three main Indian groups before European explorers arrived..?
Your answer: The Mayan, the Aztecs and the Incas were the three main Indian groups before European explorers arrived.
Hope this helps!