For a cubic crystal structure which one of the following relations indicting the cell characteristic is correct :-

Question

( A ) $a = b = c$ and $\alpha = \beta = \gamma = 90^{\circ}$
( B ) $a \neq b \neq c$ and $\alpha \neq \beta$ and $\gamma \neq 90^{\circ}$
( C ) $a = b = c$ and and $\alpha \neq \beta \neq \gamma = 90^{\circ}$
( D ) $a \neq b \neq c$ and $\alpha = \beta = \gamma = 90^{\circ}$