Which of the Following Best Explains Why Angular, Crack-Bounded, Granitic

Multiple Choice

Which of the following best explains why angular, crack-bounded, granitic blocks weather to spheroidal boulders?

A) Weathering agents have more direct access to edges and corners than to other parts of the block.
B) Interiors of blocks are constantly damp or wet because sunlight cannot penetrate.
C) Crack surfaces of blocks heat and cool more rapidly than edges and corners.
D) They slowly roll over in place and wear off the corners first.