Each of the following options contains a set of four molecules. Identify the option(s) where all four molecules possess permanent dipole moment at room temperature.

Options

A. `BF_(3), O_(3), SF_(6), XeF_(6)`
B. `BeCl_(2), CO_(2), BCl_(3), CHCl_(3)`
C. `NO_(2), NH_(3), POCl_(3), CH_(3)Cl`
D. `SO_(2), C_(6)H_(5)Cl, H_(2)Se, BrF_(5)`

Explanation

To determine which option contains four molecules that all possess a permanent dipole moment at room temperature, we will analyze each molecule in the given options. A molecule has a permanent dipole moment if it has an asymmetric distribution of charge, leading to a net dipole moment.

### Step-by-Step Solution:

1. **Analyze Option A: BF3, O3, SF6**
- **BF3 (Boron Trifluoride)**: This molecule has a trigonal planar shape and is symmetrical. The dipole moments of the B-F bonds cancel each other out, resulting in a net dipole moment of zero. **(Non-polar)**
- **O3 (Ozone)**: Ozone has a bent shape due to the presence of a lone pair on the central oxygen. The dipole moments do not cancel out, resulting in a net dipole moment. **(Polar)**
- **SF6 (Sulfur Hexafluoride)**: This molecule has an octahedral shape and is symmetrical. The dipole moments of the S-F bonds cancel each other out, resulting in a net dipole moment of zero. **(Non-polar)**
- **Conclusion for Option A**: Not all molecules have a permanent dipole moment.

2. **Analyze Option B: BeCl2, CO2, BCl3, BF3**
- **BeCl2 (Beryllium Dichloride)**: This molecule has a linear shape and is symmetrical. The dipole moments cancel out. **(Non-polar)**
- **CO2 (Carbon Dioxide)**: This molecule is also linear and symmetrical, leading to a cancellation of dipole moments. **(Non-polar)**
- **BCl3 (Boron Trichloride)**: This molecule has a trigonal planar shape and is symmetrical. The dipole moments cancel out. **(Non-polar)**
- **BF3 (Boron Trifluoride)**: As previously analyzed, it is non-polar. **(Non-polar)**
- **Conclusion for Option B**: Not all molecules have a permanent dipole moment.

3. **Analyze Option C: NO2, NH3, POCl3, CHCl3**
- **NO2 (Nitrogen Dioxide)**: This molecule has a bent shape due to the presence of a lone electron on nitrogen, resulting in a net dipole moment. **(Polar)**
- **NH3 (Ammonia)**: This molecule has a trigonal pyramidal shape due to the lone pair on nitrogen, leading to a net dipole moment. **(Polar)**
- **POCl3 (Phosphorus Oxychloride)**: This molecule has a tetrahedral shape with a double bond to oxygen and single bonds to chlorine, resulting in a net dipole moment. **(Polar)**
- **CHCl3 (Chloroform)**: This molecule has a tetrahedral shape with three chlorine atoms and one hydrogen, leading to a net dipole moment. **(Polar)**
- **Conclusion for Option C**: All molecules have a permanent dipole moment.

4. **Analyze Option D: SO2, C6H5Cl, H2S, BrF5**
- **SO2 (Sulfur Dioxide)**: This molecule has a bent shape due to the presence of a lone pair on sulfur, resulting in a net dipole moment. **(Polar)**
- **C6H5Cl (Chlorobenzene)**: This molecule has a polar bond due to the electronegativity difference between carbon and chlorine, resulting in a net dipole moment. **(Polar)**
- **H2S (Hydrogen Sulfide)**: This molecule has a bent shape due to the presence of lone pairs on sulfur, resulting in a net dipole moment. **(Polar)**
- **BrF5 (Bromine Pentafluoride)**: This molecule has a square pyramidal shape and is polar due to the asymmetry of the fluorine atoms around bromine. **(Polar)**
- **Conclusion for Option D**: All molecules have a permanent dipole moment.

### Final Conclusion:
The options where all four molecules possess a permanent dipole moment at room temperature are **Option C (NO2, NH3, POCl3, CHCl3)** and **Option D (SO2, C6H5Cl, H2S, BrF5)**.

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