Explanation: Antenna gain and beamwidth are inversely related. Gain measures how effectively an antenna concentrates radiated power in a particular direction compared to an isotropic (omnidirectional) antenna. To achieve higher gain, an antenna must focus its radio energy into a narrower angular spread. Imagine a flashlight: a wide beam spreads light over a large area (low gain), while a tightly focused beam directs intense light in one specific direction (high gain). Similarly, for radio waves, increased gain means the antenna is directing more of its available power into a smaller segment of space. This concentration of energy into a smaller angular area is precisely what a decreased beamwidth signifies. Therefore, as the gain of an antenna is increased, its beamwidth must decrease to focus the energy more effectively. Options A, B, and C are incorrect because they suggest either an increase in beamwidth or no effect, which contradicts the fundamental principle of how antennas achieve higher gain.