Which of the following types of antenna offers the greatest gain?

A Yagi antenna is a directional antenna that focuses radio energy in a specific direction, which provides significant gain compared to omnidirectional antennas. It achieves this by using multiple elements (a driven element, a reflector, and one or more directors) to shape the radiation pattern. The other options offer much less gain. A 5/8 wave vertical and a J-pole are omnidirectional antennas with only modest gain. An isotropic antenna is a theoretical point source that radiates equally in all directions, offering zero gain (0 dBi) and serving only as a mathematical reference point.