What is the relationship between the axial angles in an orthorhombic crystal system?

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