Answer:
B. Digital signals are more secure
Step-by-step explanation:
You want to know an advantage of transmitting information using digital signals.
Digital signals
Digital signals are characterized by having a few discrete states. In the simplest case, those states are {transmitting, not transmitting}. Modern digital signals are often transmitted using numerous combinations of phases, frequencies, and amplitudes.
Analog signals
Analog signals are characterized by a continuum of the characteristic used to convey the information. When amplitude modulation is used, the information of interest is conveyed by the amplitude of the signal. Similarly, when frequency or phase modulation is used, the information is conveyed by the frequency or phase of the signal, respectively.
That is, analog signals have a continuous range of values.
Distance
Any signal that is broadcast will have a signal level that decreases with distance from the source of the broadcast. Any signal conveyed through a medium will be subjected to distortions and losses due to the interaction of the signal and the medium. Hence all signals become weaker as the distance from the source increases.
Noise
The receiver of a signal will, in general, receive signals other than the one intended. These are referred to as "noise." A transmission channel may have many sources of noise, including other transmitters, Cosmic Background Radiation, thermal noise in the components of the receiver or transmission medium, and others.
For analog signals, noise can directly affect the amplitude or phase being used to represent the signal of interest. Hence it changes the received value so it is not the same as the transmitted value.
The states of digital signals are designed to be sufficiently far apart that any corruption by noise will not affect the value as interpreted by the receiver. Thus, in terms of corruption of the information, we can say digital signals are more secure.
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Additional comment
In radio transmission, noise is generally an addition to the signal. The weaker the analog signal, the greater the effect of noise. Broadcast radio began as AM radio: amplitude modulated. As the signal weakens, noise becomes a greater portion of the amplitude, so the receiver hears "static" where they want to hear voice or music.
FM, frequency modulated, radio replaced AM radio in order to avoid this issue with noise. The frequency of a signal is less likely to be corrupted. However, as the signal weakens, it can be difficult to determine its frequency, so that method of analog transmission also succumbs to noise.
Digital transmission in a noisy channel can also be corrupted by noise. Ultimately, the rate of information transmission in a given channel depends on the channel bandwidth and the signal-to-noise ratio. The integrity of a signal can be improved through coding that allows missing or corrupted bits of information to be determined based on the other bits that are received.
"Security" of a transmission can have different meanings. Here, we understand it to refer to the integrity of the information being conveyed. It could also relate to the difficulty of intercepting the transmission, or the difficulty of understanding the meaning of the received signal. Digital signals may or may not be more "secure" in these other meanings of the word.