Answer:
Magma from Venus's mantle erupted as lava.
Step-by-step explanation:
I think option C is correct because magma or lava is a molten or semi-molten material that is found under the surface of planet and volcano is the only source through which this molten material can come on the surface. For example, magma beneath the earth's surface come out through the vent of volcanoes present on earth's surface such as Mount Fuji, Barren island, etc. that's the reason why presence of magma over Venus's surface can explain the presence of volcanoes on the planet.