In which of the following structures all the bonds are present at `90^@`?

Options

A. Trigonal planar
B. tetrahedral
C. trigonal bipyramidal
D. octahedral

Answer

To determine in which of the given structures all the bonds are present at `90°`, we need to analyze the bond angles in different molecular geometries.

### Step-by-Step Solution:

1. **Understanding Molecular Geometries**:
- We need to identify the molecular geometries and their corresponding bond angles. The common geometries to consider are:
- Trigonal planar
- Tetrahedral
- Trigonal bipyramidal
- Octahedral

2. **Analyzing Trigonal Planar**:
- In a trigonal planar geometry, such as in BCl3, the bond angles are `120°`. Therefore, this structure does not have all bonds at `90°`.

3. **Analyzing Tetrahedral**:
- In a tetrahedral geometry, such as in CH4 (methane), the bond angles are `109.5°`. Thus, this structure also does not have all bonds at `90°`.

4. **Analyzing Trigonal Bipyramidal**:
- In a trigonal bipyramidal geometry, such as in PCl5, there are two types of bond angles: `120°` in the equatorial plane and `90°` between the axial and equatorial positions. However, since not all bonds are at `90°`, this structure does not meet the requirement.

5. **Analyzing Octahedral Geometry**:
- In an octahedral geometry, such as in SF6, there are six atoms arranged around a central atom. The bond angles between all adjacent bonds are `90°`. This means that all bonds in this structure are at `90°`.

6. **Conclusion**:
- The only structure where all the bonds are present at `90°` is the octahedral structure.

### Final Answer:
The structure in which all the bonds are present at `90°` is the **octahedral structure**.