We do not transmit low frequency signal to long distances because
(a) The size of the antenna should be comparablee to signal wavelength which is unreal solution for a signal of longer wavelength .
(b) Effective power radiated by a long wavelength base and signal would be high .
(c ) We want to avoid mixing up signals transmitted by different transmitter simultaneously .
(d) Low frequency signal can be sent to long distances by superimposing with a high frequency wave as well .
Therefore , the most suitable option will be :

Options

A. All statements are true
B. (a),(b) and (c ) are true only
C. (a),(c )and (d) are true only
D. (b) , (c ) and (d) are true only

Answer

To solve the question of why low frequency signals are not transmitted over long distances, we need to analyze each of the provided options carefully.

### Step 1: Analyze Option A
- **Statement**: The size of the antenna should be comparable to the signal wavelength, which is an unrealistic solution for a signal of longer wavelength.
- **Analysis**: This statement is true. For low frequency signals, the wavelength is long, which means the antenna size needs to be very large. Practically, this is not feasible, making this option a valid reason.

### Step 2: Analyze Option B
- **Statement**: Effective power radiated by a long wavelength base signal would be high.
- **Analysis**: This statement is false. In fact, the effective power radiated decreases with increasing wavelength. Therefore, this option does not provide a valid reason for not transmitting low frequency signals over long distances.

### Step 3: Analyze Option C
- **Statement**: We want to avoid mixing up signals transmitted by different transmitters simultaneously.
- **Analysis**: While it is true that mixing signals can be an issue, this is not a primary reason for not transmitting low frequency signals over long distances. Thus, this option is not the most suitable reason.

### Step 4: Analyze Option D
- **Statement**: Low frequency signals can be sent to long distances by superimposing with a high frequency wave as well.
- **Analysis**: This statement is true in the context of modulation techniques (like AM radio), where low frequency signals can be transmitted effectively by modulating them onto a high frequency carrier wave. However, it does not explain why low frequency signals are not transmitted directly over long distances.

### Conclusion
After analyzing all the options, the most suitable reason for not transmitting low frequency signals over long distances is given in **Option A**. The requirement for large antennas makes it impractical to transmit low frequency signals directly.

### Final Answer
The most suitable option is: **(a) The size of the antenna should be comparable to signal wavelength which is an unreal solution for a signal of longer wavelength.**

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