Which question is most important while checking the feasibility of a business idea?

Correct answer: Are customers willing to pay for solving the problem

Feasibility asks whether a business idea can work in practice and be sustained. A central question is whether a sufficiently large group of customers has the problem and is willing to pay for the proposed solution. A long name, the owner’s fame, or music in the shop may sometimes matter, but none establishes demand or commercial viability. Therefore A is most important.