Statement-I : Television signals are received through sky-wave propagation
Statement-II : The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false

Explanation

To solve the question, we need to analyze both statements provided:

**Statement-I**: Television signals are received through sky-wave propagation.
**Statement-II**: The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.

### Step-by-Step Solution:

1. **Understanding Sky-Wave Propagation**:
- Sky-wave propagation refers to the transmission of radio waves that are reflected back to Earth by the ionosphere. This method is effective for certain frequency ranges.
- The typical frequency range that can be reflected by the ionosphere is between 2 MHz and 30 MHz.

**Hint**: Remember that sky-wave propagation is limited to specific frequency ranges due to the properties of the ionosphere.

2. **Analyzing Television Signals**:
- Television signals typically operate at frequencies greater than 30 MHz. Since these frequencies exceed the upper limit of the sky-wave propagation range, they cannot be effectively reflected back by the ionosphere.
- Therefore, television signals cannot be received through sky-wave propagation.

**Hint**: Consider the frequency range of television signals and how it relates to the capabilities of the ionosphere.

3. **Understanding Critical Frequency**:
- The critical frequency is defined as the maximum frequency that can be reflected by the ionosphere when transmitted vertically. Frequencies above this critical frequency will penetrate the ionosphere instead of being reflected back.
- Thus, the ionosphere does not reflect electromagnetic waves of frequencies greater than the critical frequency.

**Hint**: The critical frequency is a threshold; frequencies above it will not be reflected.

4. **Evaluating Statement-II**:
- Statement-II claims that the ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency. This is incorrect because, by definition, frequencies greater than the critical frequency cannot be reflected; they penetrate the ionosphere.
- Therefore, Statement-II is also false.

**Hint**: Revisit the definition of critical frequency and its implications on wave propagation.

5. **Conclusion**:
- Both Statement-I and Statement-II are false. Hence, the correct answer is that both statements are incorrect.

### Final Answer:
Both Statement-I and Statement-II are false.