Which of the following statements is true?

a$.$ Pump and compressor are two different names for the same thing.

b$.$ If a system is at steady state, you must start with the time$-$independent form of the generalized energy balance. The time dependent form of the equation will not work.

c$.$ If the system is a heat exchanger, $Q^{}$ will always be negative by our sign convention.

d$.$ If the system is a turbine, $W_s^{}$ will always be negative by our sign convention.

e$.$ None of the above statements are true.