The curvature of diffuser vane shall be so fixed that the fluid enters the guide passage with minimum loss. This is possible only when

A. the guide vane inlet angle is always less than $$\frac{\pi }{2}$$ rad

B. the diffuser vane entrances angles are laid at same radii for a constant pitch

C. the outlet velocity angle has tangential component only

D. angle between guide vane inlet and the direction of the absolute velocity of air leaving the impeller is small or equal to

Answer: Option D