Question

how are igneous rocks classified?
by color
by the degree of foliation
by texture and composition
by cooling rate

Explanation:

Igneous rocks are primarily classified based on their texture (such as coarse - grained, fine - grained) and composition (mineral content). Color is not a primary classification factor. Foliation is related to metamorphic rocks, not igneous rocks. Cooling rate affects texture but is part of texture - based classification. Overall, texture and composition are key.

Answer:

by texture and composition