Option 1 -> The quantities purchased are choices made within the budget set, not determinants of it.
Option 2 -> Changes in both prices alter the budget constraint equation, shifting the budget set.
Option 3 -> Income changes shift the budget line parallel, expanding or contracting the budget set.
Option 4 -> Changing one price rotates the budget line, modifying the budget set.
Hence, Option 1: Change in quantities of goods purchased by the consumer -> The budget set represents all possible combinations of goods a consumer CAN afford given their income and market prices. It is determined by the budget constraint: p₁x₁ + p₂x₂ ≤ M, where prices (p₁, p₂) and income (M) are the parameters. The quantities (x₁, x₂) that the consumer actually chooses to purchase are points within the budget set, not factors that define it. Changing consumption choices simply means moving from one point to another within the same budget set, without altering the set itself. -> correct