Observe the Image of the Individual Walking Through the Lava

Multiple Choice

Observe the image of the individual walking through the lava tube. Why is it hollow there and not solid rock?

A) The inside of the lava tube was granite, but granite is not resistant to weathering, so has long since eroded away.
B) There are no natural openings within a lava flow. This must be a manmade feature.
C) When lava cools it contracts, leaving large gaps in the middle.
D) Lava on the inside of the tube often remains molten while the outside crystallizes. Sometimes that molten lava flows out, leaving an empty interior.