The correct answer is - A) extrusive.
The extrusive igneous rocks, and the type of igneous rocks that are forming on the surface or very close to the surface. This type of igneous rocks are forming very quickly because the magma is cooling down very quickly, thus giving them some specific characteristics.
These types of rocks can be easily distinguished from the intrusive rocks, the extrusive ones, because of the quick formation, have very small crystals, almost unnoticeable, while the intrusive ones, because they have much bigger period of formation, have nicely formed, easily noticeable, big crystals.
