(a) Plutonic rock
(b) Hypabyssal rock
(c) Volcanic igneous rock
(d) None of these

Ans. (a) : Plutonic rock

• Syenite is an intrusive rock, belonging to the alkali series of intermediate plutonic rocks.
• A class of intrusive igneous rocks essentially composed of an alkali, feldspar and a ferro magnesium mineral.
• A special group of alkali syenites is characterized by the pressure of a feldspathoid mineral such as nepheline, lencite, cancrinite or sodalite.