The most common volcanic rock found in lava flows on composite volcanoes is:

A) andesite
B) basalt
C) obsidian

Andesite

A volcanic rock of intermediate composition, typically grey or bluish-grey, composed mainly of plagioclase and one or more mafic minerals.

Composite Volcanoes

Also known as stratovolcanoes, are large, symmetrical volcanoes composed of alternating layers of explosive ash and lava flows, often characterized by a conical shape.