Control Systems
The output of the system has an effect upon the input quantity, then the system is a

 open loop control system.
None of these
 either 1 or 2.
 closed loop control system.

ANSWER DOWNLOAD EXAMIANS APP

Control Systems
A cascade of three linear time invariant systems is causal and unstable. From this we conclude that

 at least one system is unstable and at least one system is causal.
 at least one system is causal and all systems are unstable.
 the majority are unstable and the majority are causal.
 each system in the cascade is individually caused and unstable.

ANSWER DOWNLOAD EXAMIANS APP