Prospective candidates have to prove that they have sufficient money to cover their . . . . . . . and tuition.

The correct answer is: D. maintenance.

Maintenance is the act of keeping something in good condition. In the context of the question, it refers to the cost of living expenses, such as food, housing, and transportation.

Boarding is the act of providing food and lodging for someone. Lodging is the act of providing accommodation for someone, typically in a rented room or house. Sustenance is the act of providing the means of supporting life, such as food and drink.

While all of these options are related to the cost of living, maintenance is the most comprehensive term. It includes the cost of food, housing, transportation, and other essential expenses.