How would a geologist identify an igneous rock as extrusive?

A.
An extrusive rock is coarse-grained because it cooled slowly beneath the earth’s surface.

B.
An extrusive rock is fine-grained because it cooled quickly on the earth’s surface.

C.
An extrusive rock is fine-grained because it cooled quickly beneath the earth’s surface.

D.
An extrusive rock is coarse-grained because it cooled slowly on the earth’s surface.