Igneous rock is considered extrusive or intrusive based on:
a. how many holes the rocks contain
b. the crystalline structure of the rock particles
c. whether they were formed by cooling above or below the earth’s surface.
d. if they formed from magma or sediments

The answer is letter c. whether they were formed by cooling above or below earth's surface. 
 
 Igneous rock is considered extrusive or intrusive based on whether they were formed by cooling above or below earth's surface. It may form with or without crystallization. Igneous rock is one of the three main rock types. 

The answer is b im not sure 

Answer( solar wind );