Parent and Subsidiary Corporations Form an Affiliated Group

Parent and Subsidiary Corporations form an affiliated group. In 2018, the initial year of operation, Parent and Subsidiary filed separate returns. In 2019, the group files a consolidated tax return. The results for 2018 and 2019 are: Taxable Income
How much of Subsidiary's loss can be carried back to last year?

A) $0
B) $20,000
C) $25,000
D) none of the above