Which radio frequency propagation method allows signals to bend around obstacles?

The correct choice is the method that allows signals to bend around obstacles, which is known as Non-Line of Sight propagation. This technique is particularly useful in environments where direct communication between transmitter and receiver is hindered by physical barriers such as buildings, hills, or trees.

Non-Line of Sight propagation relies on various mechanisms, such as diffraction and reflection, which enable the radio waves to navigate around obstacles rather than traveling in a straight line. This allows for better communication in urban or rugged terrains where direct line-of-sight communication is not possible.

By contrast, the other methods do not effectively handle situations involving barriers. Ground Wave propagation follows the Earth's surface and is limited to lower frequencies, making it unsuitable for high-frequency signals in obstructed environments. Line of Sight requires an unobstructed path between transmitter and receiver, which is not always feasible. Sky Wave propagation involves the reflection of signals off the ionosphere; while it can cover long distances, it is also less effective when significant obstacles are present in the immediate environment.