Which of the following is correct?
`{:(,"Crystal system","Axial distance","Axial angles","Examples"),((1),"Cubic",aneb=c,alpha=betane gamma=90^(@),Cu","KCI),((2),"Monoclinic",aneb=c,alpha=beta=gamma=90^(@),PbCrO_(2)","PbCrO_(4)),((3),"Rhombohedral",a=b=c,alpha=beta=gammane90^(@),CaCO_(3)","NaNO_(3)),((4),"Triclinic",a=b=c,alphanebeta=gammane90^(@),K_(2)Cr_(2)O_(7)","CuSO_(4)","5H_(2)O):}`

Answer

To determine which of the given crystal systems is correct based on the provided data, we will analyze each option step by step.

### Step 1: Analyze the Cubic System
- **Given Data**: a = b = c, α = β = γ = 90°
- **Correctness Check**: In a cubic crystal system, all three edge lengths (a, b, c) are equal and all angles (α, β, γ) are 90°.
- **Conclusion**: The statement for the cubic system is correct.

### Step 2: Analyze the Monoclinic System
- **Given Data**: a ≠ b = c, α = β = γ = 90°
- **Correctness Check**: In a monoclinic system, two edge lengths are equal (b = c), and the angles α and γ are 90°, while β is not equal to 90°.
- **Conclusion**: The statement for the monoclinic system is incorrect.

### Step 3: Analyze the Rhombohedral System
- **Given Data**: a = b = c, α = β = γ ≠ 90°
- **Correctness Check**: In a rhombohedral system, all edge lengths are equal (a = b = c), and all angles (α, β, γ) are equal but not equal to 90°.
- **Conclusion**: The statement for the rhombohedral system is correct.

### Step 4: Analyze the Triclinic System
- **Given Data**: a ≠ b ≠ c, α ≠ β ≠ γ ≠ 90°
- **Correctness Check**: In a triclinic system, all three edge lengths are different, and none of the angles are equal to 90°.
- **Conclusion**: The statement for the triclinic system is correct.

### Final Conclusion
Based on the analysis:
1. **Cubic**: Correct
2. **Monoclinic**: Incorrect
3. **Rhombohedral**: Correct
4. **Triclinic**: Correct

Thus, the correct options are Cubic, Rhombohedral, and Triclinic.