The correct answer is a directional antenna. Directional antennas focus the signal in a specific direction, which increases the effective power in that direction and can provide better range and reduce interference. Omni-directional antennas, in contrast, radiate signal more uniformly in all directions, which is not suitable for point-to-point links over long distances due to weaker signals in the desired direction. Sector antennas are also directional, but with a wider beamwidth compared to the antennas used for point-to-point links, making them less effective for the described scenario.