Concept:A line of symmetry divides a figure into two mirror-image halves.Explanation:A rectangle has exactly 2 lines of symmetry.One line is vertical, passing through the midpoints of the top and bottom sides.The other line is horizontal, passing through the midpoints of the left and right sides.Folding along either line makes both halves match exactly.The diagonals of a rectangle are not lines of symmetry, because folding along a diagonal does not produce matching halves unless the rectangle is a square.Answer:C. 2