Triclinic crystal has the following unit cell parameters :

• A

  $\mathrm{a}=\mathrm{b}=\mathrm{c};\mathrm{\alpha }=\mathrm{\beta }=\mathrm{\gamma }={90}^{\circ }$

• B

  $\mathrm{a}=\mathrm{b}\ne \mathrm{c};\mathrm{\alpha }=\mathrm{\beta }=\mathrm{\gamma }={90}^{\circ }$

• C

  $\mathrm{a}\ne \mathrm{b}\ne \mathrm{c};\mathrm{\alpha }\ne \mathrm{\beta }\ne \mathrm{\gamma }\ne {90}^{\circ }$

• D

  $\mathrm{a}=\mathrm{b}\ne \mathrm{c};\mathrm{\alpha }=\mathrm{\beta }={90}^{\circ },\mathrm{\gamma }={120}^{\circ }$