Tech A says that the piston on a brake caliper that integrates the parking brake will need to be screwed back in on the threaded shaft to retract it into the bore. Tech B says that you need a special tool that mates to slots, grooves, or holes in the outer face of the caliper piston. Who is correct

Acompressor compresses a gas, a pump compresses a liquid. for a given pressure ratio, why does it take more work to compress a gas in a compressor than a liquid in a pump? a)- for a given pressure ratio the average specific volume for a gas is much higher than the average specific volume for a liquid. b)- there is no difference. the only difference is the amount of heat generated (not work) c)- for a given pressure ratio the average volurge for a gas is much higher than the average volume for a liquid. d)-there is no difference