The correct answer is B: Absorption. Vegetation (trees, leaves, etc.) absorbs UHF and microwave signals, reducing signal strength. This is because water in the vegetation absorbs radio energy at these frequencies. UHF and microwave frequencies are particularly affected by water content. Since vegetation contains significant water, it acts as an absorber, converting the radio energy into heat. This is why UHF/microwave signals are weaker when antennas are near trees or when signals must pass through vegetation. The higher the frequency, the more pronounced this effect becomes. This is one reason why UHF/microwave antennas are often mounted high and clear of trees.