411. Multistage compression is necessary for high efficiency,

A. If the ratio of the delivery pressure to the intake pressure exceeds 5:1
B. When large amount of gas is to be compressed
C. When the delivered gas is desired at very high velocity
D. None of these
✅ The correct answer is option A.

417. The laminar boundary layer thickness in zero pressure gradient flow over a flat plate along the x-direction varies as x0.5 while the thickness of turbulent boundary layer varies as (where, x = distance from the leading edge)

A. X1.5
B. X0.8
C. X-1.5
D. X-0.8
✅ The correct answer is option B.