The expected answers were:
(a)An open loop system is one in which the desired output is set by
means of an input signal, and it is assured that the output will
remain at the desired level irrespective of variations either within
the system or in the load or demand placed on the system.
(b) Block diagram of a negative feedback closed loop control system
(e)Two advantages of closed loop over open loop system:
(i) stability in system operation;
(ii)smooth system operation.