Answer:
C. Magma chamber
Step-by-step explanation:
A magma chamber is a geological feature that lies below an active volcano.
Magma chamber is a pool of magma which sits below an active volcano and feeds it with molten rocks through volcanic pipes or fracture within the earth. It is the source of magma for the volcanic process.
A caldera is a landform which which is formed as a result of the collapse of a volcano. It extends to a few kilometers in diameter.
A subduction zone is a convergent plate margin in which the denser plate goes beneath the lighter one. An example is an oceanic crust going beneath the continental crust due to its higher density.