In the reaction sequence
`CH_(2)=CH_(2) overset("hydrochlorous")underset("acid")rarr A overset(R)rarr overset(CH_(2)OH)underset(CH_(2)OH)("| ")`
`A` and `R` are respectively

Options

A.
B. `CH_(3)CH_(2)Cl and NaOH`
C. `CH_(3)CH_(2)OH and H_(2)SO_(4)`
D. `CH_(2)ClCH_(2)OH and NaHCO_(3)`

Explanation

To solve the question, we need to identify the compounds A and R in the given reaction sequence. Let's break it down step by step.

### Step 1: Identify the starting compound
The starting compound is ethylene (CH₂=CH₂), which is an alkene.

### Step 2: Reaction with Hydrochlorous acid
When ethylene reacts with hydrochlorous acid (HOCl), it undergoes an electrophilic addition reaction. The double bond in ethylene opens up, allowing the addition of the components of hydrochlorous acid.

1. The Cl atom from HOCl acts as an electrophile and adds to one of the carbon atoms.
2. The OH group from HOCl adds to the other carbon atom.

The product of this reaction is 2-chloroethanol (A):
\[ \text{A} = \text{CH}_2\text{Cl-CH}_2\text{OH} \]

### Step 3: Identify the next reaction
The next part of the sequence indicates that we have 2-chloroethanol (A) reacting with a reagent R to yield a product that has two hydroxyl (OH) groups.

### Step 4: Reaction of A with R
To convert 2-chloroethanol into a compound with two hydroxyl groups, we need to replace the Cl atom with an OH group. This can be achieved by using sodium bicarbonate (NaHCO₃) as the reagent R.

1. The sodium bicarbonate provides a hydroxide ion (OH⁻) which can attack the carbon atom bonded to Cl.
2. This results in the substitution of Cl with OH, yielding ethylene glycol (R):
\[ \text{R} = \text{CH}_2\text{OH-CH}_2\text{OH} \]

### Final Answer
Thus, the compounds A and R are:
- **A**: 2-chloroethanol (CH₂Cl-CH₂OH)
- **R**: Ethylene glycol (CH₂OH-CH₂OH)