In a tetragonal crystal :-

• A
  $ \alpha = \beta = 90^\circ \neq \gamma; a = b = c $
• B
  $ \alpha = \beta = \gamma = 90^\circ; a = b \neq c $
• C
  $ \alpha = \beta = \gamma = 90^\circ; a \neq b \neq c $
• D
  $ \alpha = \beta = 90^\circ; \gamma = 120^\circ; a = b \neq c $