Three different reactions involve a single reactant converting to products. Reaction A has a half-life that is independent of the initial concentration of the reactant, reaction B has a half-life that doubles when the initial concentration of the reactant doubles, and reaction C has a half-life that doubles when the initial concentration of the reactant is halved. Which statement is most consistent with these observations?

a. Reaction A is first order; reaction B is second order; and reaction C is zero order.

b. Reaction A is first order; reaction B is zero order; and reaction C is zero order.

c. Reaction A is zero order; reaction B is first order; and reaction C is second order.

d. Reaction A is second order; reaction B is first order; and reaction C is zero order.