The correct answer is: E. all of the above.
When a wave propagates on a transmission line, it suffers reflection several times at the sending end, the load end, and any tappings along the line. This is because the wave encounters a change in impedance at each of these points. The impedance of a transmission line is the ratio of the voltage to the current. When the wave encounters a change in impedance, some of the wave is reflected back in the direction from which it came.
The amount of reflection that occurs depends on the difference between the impedance of the transmission line and the impedance of the load. If the impedances are matched, there will be no reflection. However, if the impedances are not matched, some of the wave will be reflected back.
The reflection of the wave can cause problems in transmission lines. For example, it can cause standing waves to form, which can reduce the power that is transmitted to the load. To avoid these problems, it is important to match the impedance of the transmission line to the impedance of the load.
Tappings are points along the transmission line where a connection is made to another circuit. When a wave encounters a tapping, some of the wave is transmitted to the other circuit and some of the wave is reflected back. The amount of reflection that occurs depends on the impedance of the tapping and the impedance of the transmission line.
The reflection of the wave at a tapping can cause problems in transmission lines. For example, it can cause standing waves to form, which can reduce the power that is transmitted to the load. To avoid these problems, it is important to match the impedance of the tapping to the impedance of the transmission line.