The addition of HCl to an alkene proceeds in two steps. The first step is the attack of `H^(+)` ion to `gt C = C lt` portion which can be shown as

Options

A.
B.
C.
D. All of these are possible

Explanation

To solve the problem regarding the addition of HCl to an alkene, we can break down the process into clear steps:

### Step 1: Identify the Alkene
Let's denote the alkene as R-CH=CH2, where R represents any alkyl group.

### Step 2: Protonation of the Alkene
In the first step of the reaction, the H⁺ ion from HCl attacks the alkene. The alkene has a double bond (C=C), which consists of a sigma bond and a pi bond. The pi bond is electron-rich and can act as a nucleophile.

### Step 3: Formation of a Carbocation
When the H⁺ ion attacks one of the carbon atoms in the double bond, it results in the breaking of the pi bond. This leads to the formation of a carbocation on the other carbon atom. The reaction can be illustrated as follows:

1. The pi electrons from the C=C bond are used to bond with the H⁺ ion.
2. The carbon that receives the H⁺ becomes positively charged (carbocation).
3. The other carbon now has only a single bond and is left with a positive charge.

The reaction can be represented as:
\[ R-CH=CH_2 + H^+ \rightarrow R-CH^+-CH_3 \]

### Step 4: Resulting Intermediate
The intermediate formed is a carbocation (R-CH⁺-CH3), which is a key species in the addition reaction.

### Step 5: Subsequent Step (Not Required by the Question)
Although not explicitly asked, the next step would involve the attack of the Cl⁻ ion on the carbocation to form the final product (alkyl chloride).

### Summary of the Steps:
1. Identify the alkene structure.
2. Protonation of the alkene by H⁺.
3. Formation of a carbocation.
4. (Optional) Attack of Cl⁻ to form the final product.