While exploring an ancient lava field, a geologist discovers a piece of granite that has a coating of soft, crumbling rust. What is the most likely explanation for this rust? A.
Exposure to air has caused the iron-bearing minerals in the granite to oxidize.
B.
At some point in the past, a river flowed over the field, depositing the rust on top of the granite.
C.
Exposure to acid precipitation has worn away the granite's exterior, revealing its soft interior.
D.
Snails and fungi living in the lava field have secreted chemicals that reacted with the granite to form rust.