For an orthorhombic crystal system,the axial lengths are $a \neq b \neq c$. What are the axial angles?

• A
  $\alpha = \beta = \gamma \neq 90^\circ$
• B
  $\alpha = \beta = \gamma = 90^\circ$
• C
  $\alpha = \gamma = 90^\circ, \beta = 120^\circ$
• D
  $\alpha \neq \beta \neq \gamma \neq 90^\circ$