Explanation: In vacuum tube theory, "load" refers to the component or circuit that draws power from the tube and through which the useful output signal is developed. Statement A defines this precisely: it's the impedance through which the plate current flows, creating a voltage drop that becomes the useful output, such as an amplified signal or RF power. Statement B describes the *degree* of loading. A tube delivers maximum power to its load when the load impedance matches the tube's internal plate impedance. When the load impedance is very high, little current flows, and the tube is lightly loaded. As the load impedance decreases and approaches the internal plate impedance, the tube delivers more power, and thus the "load" on the tube is said to increase. Therefore, both A and B provide correct and complementary aspects of understanding "load" in a vacuum tube circuit, making C the most accurate answer.