Answer:
B. Spending a dollar less on X and a dollar more on Y increases utility
Step-by-step explanation:
Consumer's utility maximising equilibrium in case of two commodities is when Marginal Utility on per unit currency spent on both goods is equal.
MU X / P X = MU Y / P Y
If MU X / P X < MU Y / P Y : Consumer gets more additional satisfaction per unit currency spent, from good Y than good X
So in this case, spending a dollar less on X & a dollar more on Y increases utility.