Assertion (A) IUPAC name of the compound
`CH_(3)-underset(CH_(3))underset(|)(CH)-O-CH_(2)-CH_(3)` is 2-ethoxy-2-methylethane
Reason (R) In IUPAC nonmenclature, ether is regarded as hydrocarbon derivative in which a hydrogen atom is replaced by -OR and or -OAr group [where, R = alkyl group and Ar = aryl group].

Options

A. Assertion and reason both are correct and reason is correct explanation of assertion.
B. Assertion and reasons both are wrong statements.
C. Assertion is correct statement but reasons is wrong statement.
D. Assertion is wrong statement but reason is correct statement

Explanation

To solve the question, we will analyze both the assertion and the reason provided.

### Step 1: Analyze the Compound
The given compound is `CH3-CH(CH3)-O-CH2-CH3`. We need to determine its structure and identify the longest carbon chain.

### Step 2: Identify the Longest Carbon Chain
The longest carbon chain in the compound can be identified as follows:
- The carbon atoms connected directly to each other are counted.
- In this case, the longest chain consists of three carbon atoms (propane).

### Step 3: Number the Carbon Chain
We will number the carbon chain:
1. Start from one end of the chain to minimize the numbers assigned to the substituents.
2. The carbon chain can be numbered as follows:
- CH3 (1) - CH (2) - CH2 (3)

### Step 4: Identify the Substituents
The substituent in this compound is the ethoxy group (-O-CH2-CH3). Since it is attached to the second carbon of the propane chain, we can denote it as 2-ethoxy.

### Step 5: Write the IUPAC Name
Combining the information from the previous steps, the IUPAC name of the compound is:
- 2-ethoxypropane.

### Step 6: Evaluate the Assertion
The assertion states that the IUPAC name of the compound is 2-ethoxy-2-methylethane. However, we found that the correct name is 2-ethoxypropane. Therefore, the assertion is **incorrect**.

### Step 7: Evaluate the Reason
The reason states that in IUPAC nomenclature, ethers are regarded as hydrocarbon derivatives where a hydrogen atom is replaced by an -OR or -OAr group. This statement is **correct** because it accurately describes the classification of ethers.

### Conclusion
- Assertion (A) is **incorrect**.
- Reason (R) is **correct**.

Thus, the final answer is that the assertion is wrong, but the reason is correct.