$1\mathrm{.}1$ Which of the following statements are true? For the false statements, explain why you think they are false:

$($a$)$ Feedforward and feedback control require a measured variable.

$($b$)$ For feedforward control, the measured variable is the variable to be controlled.

$($c$)$ Feedback control theoretically can provide perfect control $($i$.$e$.,$ no deviations from set point$)$ if the process model used to design the control system is perfect.

$($d$)$ Feedback control takes corrective action for all types of process disturbances, both known and unknown.

$($e$)$ Feedback control is superior to feedforward control.