lower power consumption per unit of air delivered

higher volumetric efficiency

decreased discharge temperature

all of the above.

better lubrication is possible advantages of multistage

more loss of air due to leakage past the cylinder

mechanical balance is better

air can be cooled perfectly in between

increase

decrease

remain unaffected

may increase/decrease depending on compressor clearance

slip factor

velocity factor

velocity coefficient

blade effectiveness

inlet losses

impeller channel losses

diffuser losses

all of the above