The optimum bundle of the consumer is located at the point where:

Option 1 -> Budget line and indifference curve are different concepts (a line vs. a curve) and cannot be equal.

Option 2 -> An indifference curve (a curve) cannot equal the slope of budget line (a number).

Option 3 -> At consumer equilibrium, the slope of the indifference curve (MRS) equals the slope of the budget line (price ratio) - this is the tangency condition.

Option 4 -> A slope (numerical value) cannot equal a budget line (geometric line).

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Hence, Option 3: Slope of indifference curve = Slope of budget line -> At the optimum bundle, the consumer maximizes utility subject to the budget constraint. This occurs at the tangency point where the Marginal Rate of Substitution (MRS), which is the absolute value of the slope of the indifference curve, equals the price ratio (Px/Py), which is the absolute value of the slope of the budget line. This tangency condition ensures that the consumer cannot improve their utility by reallocating their budget between goods -> correct