In tetragonal crystal system, which of following

Options

A. All axial lengths and all axial angles are equal.
B. All three axial tengths are equal.
C. All three axial angles are equal.
D. Two axial angies are equal, but the third is different.

Explanation

To solve the question regarding the tetragonal crystal system, we need to understand the characteristics of this system in terms of axial lengths and angles.

### Step-by-step Solution:

1. **Understanding Tetragonal Crystal System**:
- In a tetragonal crystal system, the relationship between the axial lengths is defined as:
- \( a = b \neq c \)
- This means that the lengths of the axes 'a' and 'b' are equal, but the length of axis 'c' is different.

2. **Axial Angles in Tetragonal System**:
- The angles between the axes in a tetragonal crystal system are:
- \( \alpha = \beta = \gamma = 90^\circ \)
- This indicates that all angles are right angles.

3. **Evaluating the Options**:
- **Option A**: "All axial lengths and all axial angles are equal."
- This is incorrect because, while the angles are equal, the lengths are not (since \( a = b \neq c \)).
- **Option B**: "All three axial lengths are equal."
- This is also incorrect because, in a tetragonal system, \( c \) is not equal to \( a \) or \( b \).
- **Option C**: "All three axial angles are equal."
- This is correct because \( \alpha = \beta = \gamma = 90^\circ \).
- **Option D**: "Two axial angles are equal."
- This is incorrect because all three angles are equal to \( 90^\circ \).

4. **Conclusion**:
- The only correct option is **C**, which states that all three axial angles are equal.

### Final Answer:
- The correct answer is **C**: All axial angles are equal.