Because these rocks cool slowly, the rocks are able to form large crystals hence giving the rock a coarse texture. These crystals are big enough to be viewed with the unaided eye. The opposite is extrusive rocks that form on the surface of the earth. These cool rapidly and form fine-grained textured rocks because of the small crystals formed during the rapid cooling process.
It should be option (A) because conduction is the transfer of heat energy from one place to another by vibrations/motion of the molecules. I hoped I helped.
