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 solve the question of identifying the options where all four molecules possess a permanent dipole moment at room temperature, we will analyze each option based on the molecular structures and their symmetry.

### Step-by-Step Solution:

1. **Understanding Permanent Dipole Moment**:
- A molecule has a permanent dipole moment if it has an asymmetrical shape or structure, leading to an uneven distribution of electron density. This results in a dipole moment that does not cancel out.
- Conversely, symmetrical molecules typically have a dipole moment of zero because the individual dipole moments cancel each other out.

2. **Analyzing Each Option**:
- **Option A**: BF3, CO2, BCl2, BCl3
- **BF3**: Symmetrical (trigonal planar), dipole moment = 0.
- **CO2**: Symmetrical (linear), dipole moment = 0.
- **BCl2**: Symmetrical (linear), dipole moment = 0.
- **BCl3**: Symmetrical (trigonal planar), dipole moment = 0.
- **Conclusion**: All molecules have a dipole moment of 0. **Not a valid option**.

- **Option B**: CO2, BCl2, BCl3, CHCl3
- **CO2**: Symmetrical (linear), dipole moment = 0.
- **BCl2**: Symmetrical (linear), dipole moment = 0.
- **BCl3**: Symmetrical (trigonal planar), dipole moment = 0.
- **CHCl3**: Asymmetrical (tetrahedral), dipole moment ≠ 0.
- **Conclusion**: CO2, BCl2, and BCl3 have dipole moments of 0. **Not a valid option**.

- **Option C**: NO2, NH3, POCl3, CH3Cl
- **NO2**: Asymmetrical (bent), dipole moment ≠ 0.
- **NH3**: Asymmetrical (trigonal pyramidal), dipole moment ≠ 0.
- **POCl3**: Asymmetrical (trigonal pyramidal), dipole moment ≠ 0.
- **CH3Cl**: Asymmetrical (tetrahedral), dipole moment ≠ 0.
- **Conclusion**: All molecules possess a permanent dipole moment. **Valid option**.

- **Option D**: SO2, ClC6H5, H2O, BrF5
- **SO2**: Asymmetrical (bent), dipole moment ≠ 0.
- **ClC6H5**: Asymmetrical (due to chlorine), dipole moment ≠ 0.
- **H2O**: Asymmetrical (bent), dipole moment ≠ 0.
- **BrF5**: Asymmetrical (square pyramidal), dipole moment ≠ 0.
- **Conclusion**: All molecules possess a permanent dipole moment. **Valid option**.

3. **Final Answer**:
- The options where all four molecules possess a permanent dipole moment at room temperature are **Option C** and **Option D**.