The most common volcano type at ocean-continent convergent boundaries are:

a. calderas

b. mid-ocean ridges

c. stratovolcanoes (composite volcanoes)

d. shield volcanoes

Answer: Option (C)

Explanation: Strato-volcanoes are conical shaped-composite volcano that are produced at the convergent plate boundary. For example, Mount Fuji.

Mid oceanic ridge form at the divergent plate boundary where new crusts are formed.

Calderas are large volcanic depressions formed when an eruption takes place and gets collapsed in its mouth.

Shield volcano is a very gently dipping volcano where the magma are of low viscosity.

Thus, the correct answer is option (C).