Option 1 -> Grammatically imprecise; should specify 'one of' the indifference curves.
Option 2 -> Correctly states that the budget line is tangent to one specific indifference curve at optimum.
Option 3 -> Grammatically and economically incorrect; a line cannot be 'equal' to curves.
Option 4 -> Confuses production (MRT) with consumption concepts; MRT is not relevant to consumer choice.
Hence, Option 2: Budget line is tangent to one of the indifference curves -> At the consumer's optimum, the budget line touches (is tangent to) the highest attainable indifference curve. At this tangency point, the slope of the budget line (price ratio -P₁/P₂) equals the slope of the indifference curve (Marginal Rate of Substitution). This ensures the consumer maximizes utility given their budget constraint. The consumer cannot reach a higher indifference curve without exceeding their budget -> correct