In dark, which of the following reacts with hydrogen

Options

A. `Br_(2)`
B. `F_(2)`
C. `I_2`
D. `Cl_(2)`

Explanation

To solve the question "In dark, which of the following reacts with hydrogen?", we will analyze the reactivity of halogens with hydrogen under dark conditions.

### Step-by-Step Solution:

1. **Identify the Reactants**: The reactants in this case are hydrogen (H₂) and halogens (X₂), where X can be fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

2. **Understand the Reaction**: The general reaction of halogens with hydrogen can be represented as:
\[ H_2 + X_2 \rightarrow 2HX \]
This means that hydrogen gas reacts with halogen gas to form hydrogen halides.

3. **Consider the Conditions**: The question specifies that the reaction occurs in the dark. This is an important condition because some halogens require light to initiate the reaction.

4. **Evaluate Each Halogen**:
- **Fluorine (F₂)**: Fluorine is highly reactive and can react with hydrogen even in the dark.
- **Chlorine (Cl₂)**: Chlorine typically requires light to initiate the reaction, so it may not react in the dark.
- **Bromine (Br₂)**: Bromine also generally requires light for the reaction to proceed.
- **Iodine (I₂)**: Iodine can react with hydrogen, but it usually requires a catalyst to do so, especially in the dark.

5. **Conclusion**: Based on the above evaluations, the only halogen that can react with hydrogen in the dark without any additional requirements is fluorine (F₂). Therefore, the answer is:
\[ \text{Fluorine (F₂)} \]

### Final Answer:
The correct option is **Fluorine (F₂)**.