In communication systems, the overall quality of signal transmission between a transmitter and a receiver depends mainly on which of the following factors?

Introduction / Context:
This question belongs to basic communication and electronics concepts that are often tested in general knowledge and entrance exams. Whenever information is sent from one place to another, the form of the signal (for example, analog or digital, strength and bandwidth) and the physical medium through which it is sent (for example, copper wire, optical fibre, air or space) determine how faithfully the original information reaches the receiver. Understanding that transmission quality is influenced by both signal characteristics and medium characteristics is essential for appreciating real world communication systems.

Given Data / Assumptions:

• The communication process involves a signal that carries information.
• The signal travels through some medium such as wire, optical fibre, or free space.
• The question asks what quality of transmission depends on.
• Options isolate the signal, the medium, both together, or neither.

Concept / Approach:
Quality of transmission is usually judged by how little the signal is distorted, attenuated or corrupted by noise when it arrives at the receiver. The nature of the signal, such as its frequency range, power level, modulation scheme and whether it is analog or digital, affects how robust it is against noise and interference. At the same time, the nature of the medium, such as its resistance, capacitance, dispersion, attenuation and susceptibility to external noise, also plays a major role. Because both aspects are crucial, engineers design communication systems by matching signal properties to the chosen medium and by selecting or improving the medium to suit the signal.

Step-by-Step Solution:
Step 1: Consider the signal itself. A weak signal with very large bandwidth may be more vulnerable to noise and distortion than a properly modulated and appropriately powerful signal. Step 2: Think about the medium. A poor quality copper cable or an air path with obstacles introduces attenuation, dispersion and interference that degrade the signal. Step 3: Observe that clearer communication can be achieved by improving the signal properties (for example, using better modulation and coding) even if the medium remains the same. Step 4: Also observe that better performance can be obtained by changing the medium (for example, moving from copper wire to optical fibre) even when the signal format is unchanged. Step 5: Conclude that both the signal and the medium together determine transmission quality, so the correct choice is the option stating that quality depends on both.

Verification / Alternative check:
A practical way to verify this is to consider a digital signal transmitted over two different media, such as an old noisy cable versus a high quality optical fibre. Even if the signal format is ideal, the bad cable will yield poor performance compared to the fibre, showing the effect of medium. Conversely, if the same fibre is used but with an extremely poorly designed signal (for example, too little power or inappropriate modulation), the received quality will still be bad. These thought experiments show that neither factor can be ignored, confirming that quality depends on both the nature of the signal and the medium.

Why Other Options Are Wrong:
Nature of the signal only is insufficient because even an excellent signal will suffer if the medium is extremely lossy or noisy. Nature of the medium only is also insufficient because a poor signal design can fail even on a high quality medium. Neither the signal nor the medium characteristics cannot be correct, because these two aspects are precisely what engineers adjust to improve communication quality.

Common Pitfalls:
Students sometimes focus only on the transmission medium, especially when they have learned about differences between copper wires, radio channels and optical fibres. Others may focus only on the signal side, such as modulation techniques or power levels. In reality, communication system design always considers both together. For exams, remember that whenever a question mentions quality of transmission in a general way, the safest complete answer is that it depends on both the nature of the signal and the nature of the medium.

Final Answer:
The quality of signal transmission depends on both the nature of the signal and the nature of the transmission medium.