Identify the correct statements with regard to the consumer's budget line/set.

(A) A decrease in the price of goods makes the budget line steeper

(B) A decrease in the price of goods makes the budget line flatter

(C) An increase in the price of goods makes the budget line steeper

(D) All bundles in the positive quadrant which are on or below the line are included in the budget set.

Option 1 -> Incorrect. A decrease in the price of the good on the horizontal axis makes the budget line flatter, not steeper.

Option 2 -> Incorrect. Statement (D) about the budget set is also correct, so this option is incomplete.

Option 3 -> Incorrect. Statement (A) is false - a price decrease makes the line flatter (for the good on x-axis), not steeper.

Option 4 -> Correct. Contains only the true statements (B), (C), and (D).

Hence, Option 4: (B), (C) and (D) only -> For a budget line with good X on the horizontal axis and good Y on the vertical axis, the slope is -Px/Py. When the price of good X decreases, the absolute value of the slope decreases, making the line flatter (statement B is correct). When the price of good X increases, the absolute value of the slope increases, making the line steeper (statement C is correct). The budget set includes all affordable bundles, which are all points on or below the budget line in the positive quadrant (statement D is correct). Statement A is incorrect because a price decrease makes the line flatter, not steeper. -> correct