The group having triangular planar structures is :

Options

A. `BF_(3), NF_(3), CO_(3)^(2-)`
B. `CO_(3)^(2-), NO_(3)^(-), SO_(3)`
C. `NH_(3), SO_(3), CO_(3)^(2-)`
D. `NCl_(3), BCl_(3), SO_(3)`

Explanation

To determine which group has triangular planar structures, we need to analyze the molecular geometry of the compounds listed in the options. The triangular planar structure is characterized by a central atom surrounded by three other atoms in a single plane, forming 120-degree angles between them.

### Step-by-Step Solution:

1. **Identify the Compounds in Each Option**:
- We need to look at the compounds provided in each option to check their molecular geometry.

2. **Analyze Option A**:
- **BF3 (Boron Trifluoride)**: Boron has three valence electrons and forms three bonds with fluorine atoms. The geometry is triangular planar.
- **NF3 (Nitrogen Trifluoride)**: Nitrogen has five valence electrons and forms three bonds with fluorine, but has one lone pair. This gives it a pyramidal shape, not triangular planar.
- Since not all compounds in option A have a triangular planar structure, option A is incorrect.

3. **Analyze Option B**:
- **CO3^2- (Carbonate Ion)**: Carbon has four valence electrons and forms bonds with three oxygen atoms, resulting in a triangular planar structure.
- **NO3^- (Nitrate Ion)**: Nitrogen has five valence electrons and forms bonds with three oxygen atoms, also resulting in a triangular planar structure.
- **SO3 (Sulfur Trioxide)**: Sulfur has six valence electrons and forms bonds with three oxygen atoms, leading to a triangular planar structure.
- All three compounds in option B have a triangular planar structure, making option B correct.

4. **Analyze Option C**:
- **NH3 (Ammonia)**: Nitrogen has five valence electrons and forms three bonds with hydrogen, but has one lone pair, giving it a pyramidal shape.
- Since NH3 is not triangular planar, option C is incorrect.

5. **Analyze Option D**:
- **NCl3 (Nitrogen Trichloride)**: Similar to NH3, nitrogen forms three bonds with chlorine and has one lone pair, resulting in a pyramidal shape.
- Since NCl3 is not triangular planar, option D is incorrect.

### Conclusion:
After analyzing all options, the only group that contains compounds with triangular planar structures is **Option B**.