Explanation: Characteristic impedance (Zo) is an intrinsic property of a transmission line, determined by its physical construction, such as the diameter of the conductors, the spacing between them, and the dielectric material separating them. These factors determine the line's inductance per unit length and capacitance per unit length. Since Zo is defined by these per-unit-length properties, cutting a transmission line in half does not change these fundamental characteristics for each resulting piece. Each half retains the same physical construction and material properties as the original line, and therefore, its characteristic impedance remains unchanged at 72 ohms. Options A and B are incorrect because Zo is not dependent on the total length of the line. Option D is incorrect because the exact length is irrelevant for determining Zo; only the physical cross-sectional geometry matters.