Hansel and Gretel, a married couple, manage apartments and they are required to live in the managers' apartment as a condition of their employment.Instead of providing the apartment to Hansel and Gretel rent-free, the owner of the apartment building gives Hansel and Gretel a housing allowance of $600, which they use to pay rent on the managers' apartment.Hansel and Gretel pay $600 per month in rent.If they did not live in the managers' apartment, Hansel and Gretel could live in another apartment building where they would only pay $500 in rent. What amount, if any, must be included in Hansel and Gretel's gross income?

A) $0

B) $100

C) $500

D) $600

Its not "B", CFP Income Tax Planning Mid-Term by Dalton says its wrong?