Answer: C. They will have more time to manage his mother's care.
Step-by-step explanation:
A single income option means that only one of them will be working and only one source of income will be used to maintain all three of them including Daniel's mother. This will most definitely result in them having less disposable income and less financial income in general.
Also the scenario painted made no mention of a baby so option D is incorrect. The most likely option in C which makes sense because with one of them staying home to take care of the mother, they will have time to be able to take care of her better.