Decreasing order of stability of following alkenes is
(i) `CH_(3)-CH=CH_(2)`
(ii) `CH_(3)-CH=CH-CH_(3)`
(iv) `CH_(3)-underset(CH_(3))underset(|)(C)=CH-CH_(3)`
(iv) `CH_(3)-overset(CH_(3))overset(|)(C)=overset(CH_(3))overset(|)(C)-CH_(3)`

Options

A. (i)>(ii)>(iii)>(iv)
B. (iv)>(iii)>(ii)>(i)
C. (iii)>(ii)>(i)>(iv)
D. (ii)>(iii)>(iv)>(i)

Explanation

To determine the decreasing order of stability of the given alkenes, we will analyze each alkene based on the number of alpha hydrogens and the degree of substitution of the double bond. The more substituted the alkene, the more stable it is due to hyperconjugation and the inductive effect.

### Step-by-Step Solution:

1. **Identify the Alkenes:**
- (i) `CH₃-CH=CH₂` (Alkene 1)
- (ii) `CH₃-CH=CH-CH₃` (Alkene 2)
- (iii) `CH₃-C(CH₃)=CH-CH₃` (Alkene 3)
- (iv) `CH₃-C(CH₃)(C)=C(CH₃)-CH₃` (Alkene 4)

2. **Determine the Number of Alpha Hydrogens:**
- **Alkene 1:**
- The double bond is between the second and third carbon. The alpha carbon (the carbon directly attached to the double bond) is `CH₃` (3 hydrogens) and `CH₂` (2 hydrogens).
- Total alpha hydrogens = 3 (from `CH₃`) + 2 (from `CH₂`) = **5 alpha hydrogens**.

- **Alkene 2:**
- The double bond is between the second and third carbon. The alpha carbons are `CH₃` (3 hydrogens) and `CH₃` (3 hydrogens).
- Total alpha hydrogens = 3 (from one `CH₃`) + 3 (from the other `CH₃`) = **6 alpha hydrogens**.

- **Alkene 3:**
- The double bond is between the second and third carbon. The alpha carbons are `CH₃` (3 hydrogens) and `C(CH₃)` (which has 3 hydrogens).
- Total alpha hydrogens = 3 (from `CH₃`) + 3 (from `C(CH₃)`) + 3 (from `CH₃` at the end) = **9 alpha hydrogens**.

- **Alkene 4:**
- The double bond is between the second and third carbon. The alpha carbons are `C(CH₃)(C)` (which has 3 + 3 + 3 hydrogens from three `CH₃` groups).
- Total alpha hydrogens = 3 (from one `CH₃`) + 3 (from another `CH₃`) + 3 (from the last `CH₃`) = **12 alpha hydrogens**.

3. **Stability Order Based on Alpha Hydrogens:**
- Alkene 4 has 12 alpha hydrogens (most stable).
- Alkene 3 has 9 alpha hydrogens.
- Alkene 2 has 6 alpha hydrogens.
- Alkene 1 has 5 alpha hydrogens (least stable).

4. **Final Order of Stability:**
- **Most Stable to Least Stable:**
- (iv) `CH₃-C(CH₃)(C)=C(CH₃)-CH₃` (12 alpha H)
- (iii) `CH₃-C(CH₃)=CH-CH₃` (9 alpha H)
- (ii) `CH₃-CH=CH-CH₃` (6 alpha H)
- (i) `CH₃-CH=CH₂` (5 alpha H)

### Conclusion:
The decreasing order of stability of the alkenes is:
**(iv) > (iii) > (ii) > (i)**