An alcohol (A) on dehydration gives (B), which on ozonolysis gives acetone and formaldehyde. (B) decolourises alkaline `KMnO_(4)` solution but (A) does not. (A) and (B) are respectively:

Options

A. `CH_(3)CH_(2)CH_(2)CH_(2)OHandCH_(2)CH_(2)CH=CH_(2)`
B. `CH_(2)CH_(2)-underset(OH)underset(|)(C)H-CH_(2)andCH_(2)-CH=CH-CH_(2)`
C. `(CH_(3))_(3)C-OHand(CH_(3))_(2)C=CH_(2)`
D. `(CH_(3))_(3)CHCH_(2)-OHand(CH_(3))_(2)C=CH_(2)`

Explanation

To solve the problem, we need to identify the compounds (A) and (B) based on the information provided. Let's break it down step by step.

### Step 1: Identify Compound B
We know that compound (B) on ozonolysis gives acetone and formaldehyde. The ozonolysis of an alkene typically breaks the double bond and adds oxygen to form carbonyl compounds.

**Acetone** has the structure:
\[ \text{CH}_3\text{C(=O)}\text{CH}_3 \]

**Formaldehyde** has the structure:
\[ \text{H}_2\text{C=O} \]

To find compound (B), we can deduce that it must be an alkene that, when ozonolyzed, produces these two carbonyl compounds. The structure of (B) should be:
\[ \text{C}_3\text{H}_6 \text{ (alkene)} \]

The most likely candidate for (B) is:
\[ \text{CH}_3\text{C=CH}_2 \]
This structure, when ozonolyzed, would yield acetone and formaldehyde.

### Step 2: Identify Compound A
Next, we know that compound (A) is an alcohol that on dehydration gives compound (B). Dehydration of an alcohol typically involves the removal of a water molecule to form an alkene.

Since we have identified (B) as \( \text{CH}_3\text{C=CH}_2 \), we can deduce that (A) must be the corresponding alcohol. The alcohol that would dehydrate to form this alkene is:
\[ \text{CH}_3\text{C(OH)(CH}_3)\text{H} \]
This is 2-butanol.

### Step 3: Verify the Properties
We also know that (B) decolorizes alkaline KMnO4 solution, indicating that it is an alkene (which can be oxidized), while (A) does not. This is consistent because alcohols do not typically decolorize KMnO4.

### Conclusion
Thus, we conclude that:
- Compound (A) is **2-butanol** (C4H10O)
- Compound (B) is **propene** (C3H6)

### Final Answer
(A) is **2-butanol** and (B) is **propene**.

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