In satellite communication
1. The frequency used lies between 5 MHz and 10 MHz.
2. The uplink and downlink frequencies are different.
3. The orbit of geostationary satellite lies in the equatorial plane at an inclination of `0^(@)`

Options

A. only 2 and 3 true
B. all are true
C. only 2 true
D. only 1 and 2 true

Answer

To solve the question regarding satellite communication, we need to evaluate each of the statements provided:

1. **The frequency used lies between 5 MHz and 10 MHz.**
2. **The uplink and downlink frequencies are different.**
3. **The orbit of geostationary satellite lies in the equatorial plane at an inclination of 0°.**

Let's analyze each statement step by step:

### Step 1: Analyze the first statement
- The statement claims that the frequency used in satellite communication lies between 5 MHz and 10 MHz.
- In reality, the frequency range for satellite communication is much higher, typically starting from around 1 GHz (1000 MHz) and going up to several GHz (for example, 40 GHz or more).
- Therefore, this statement is **false**.

### Step 2: Analyze the second statement
- The second statement asserts that the uplink and downlink frequencies are different.
- This is indeed true. In satellite communication, the uplink (the signal sent from the ground to the satellite) and downlink (the signal sent from the satellite back to the ground) frequencies are kept different to avoid interference and distortion of signals.
- For example, uplink frequencies might be in the range of 5 to 6 GHz, while downlink frequencies could be in the range of 3 to 4 GHz.
- Hence, this statement is **true**.

### Step 3: Analyze the third statement
- The third statement mentions that the orbit of a geostationary satellite lies in the equatorial plane at an inclination of 0°.
- This is also true. A geostationary satellite orbits the Earth at a height where it appears stationary relative to a point on the Earth's surface, which requires it to be positioned directly above the equator (0° inclination).
- Thus, this statement is **true**.

### Conclusion
- From the analysis:
- Statement 1 is false.
- Statement 2 is true.
- Statement 3 is true.
- Therefore, the correct answer is that **only statements 2 and 3 are true**.

### Final Answer
The correct option is that **only statements 2 and 3 are true**.

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