Courtney Sells a Cottage at the Lake That the Family

Courtney sells a cottage at the lake that the family had used for their summer vacations. The purchaser paid Courtney $100,000 and assumed the mortgage which had a principal balance of $50,000. Courtney had purchased the cottage five years ago for $170,000. Courtney will recognize

A) no gain or loss.
B) a gain of $20,000.
C) a loss of $20,000.
D) a loss of $70,000.