Cameron (Single) Purchased and Moved into His Principal Residence on July

Cameron (single) purchased and moved into his principal residence on July 1, year 1. On June 1, year 2, Cameron lost his job. Because he couldn't afford the payments on his new home, he sold it on July 1, year 2 in order to move into some apartments across the street. On the sale of his principal residence, Cameron realized a $50,000 gain. How much of the gain is Cameron allowed to exclude from his year 3 gross income?

A) $0.
B) $2,500.
C) $25,000.
D) $50,000.