Assertion. Acidity of the C-H bond decreases in the order: `HC-=CH gt H_2C =CH_2 gt CH_3 -CH_3`
Reason. Acidity of the C-H bond increases as the electronegativity of the carbon to which it is attached increases

Options

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

Answer

To solve the question regarding the acidity of C-H bonds in different hydrocarbons, we will analyze the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding Acidity in Hydrocarbons**:
- Acidity in hydrocarbons is determined by the stability of the conjugate base formed when a hydrogen atom is removed (deprotonation). The more stable the conjugate base, the stronger the acid.

2. **Identifying the Hydrocarbons**:
- We have three hydrocarbons to compare:
- **HC≡CH** (ethyne or acetylene)
- **H₂C=CH₂** (ethylene)
- **CH₃-CH₃** (ethane)

3. **Determining the Conjugate Bases**:
- When we remove a hydrogen atom from each hydrocarbon, we form the following conjugate bases:
- From HC≡CH: HC≡C⁻
- From H₂C=CH₂: H₂C=CH⁻
- From CH₃-CH₃: CH₃-CH₂⁻

4. **Analyzing Hybridization**:
- The hybridization of the carbon atoms in these hydrocarbons affects the acidity:
- HC≡CH: sp hybridized (50% s character)
- H₂C=CH₂: sp² hybridized (33% s character)
- CH₃-CH₃: sp³ hybridized (25% s character)

5. **Understanding s Character and Acidity**:
- Higher s character in hybridized orbitals means that the electrons are held closer to the nucleus, which stabilizes the negative charge on the conjugate base.
- Therefore, the order of acidity based on hybridization is:
- HC≡CH > H₂C=CH₂ > CH₃-CH₃

6. **Conclusion on Assertion**:
- The assertion that the acidity of the C-H bond decreases in the order: HC≡CH > H₂C=CH₂ > CH₃-CH₃ is correct.

7. **Evaluating the Reason**:
- The reason states that the acidity of the C-H bond increases as the electronegativity of the carbon to which it is attached increases.
- This is true because higher electronegativity means a greater ability to stabilize the negative charge on the conjugate base.

8. **Final Conclusion**:
- Both the assertion and the reason are correct, and the reason correctly explains the assertion.

### Final Answer:
- The assertion is correct, and the reason is also correct. The correct answer is option (1).