A mathematical model of a system gives a way to predict the behaviour of a system for new inputs that we have never applied to the system.

A mathematical model never perfectly describes the behaviour of a physical system.

There is always a unique best mathematical model for a system.

There is often a trade-off between how well a model describes a system and how easy it is to analyse the model mathematically.

116.30%

16.30%

5.82%

581.52%

G_{re}(s) = \frac{1}{1-P(s)C(s)}

G_{re}(s) = \frac{F(s)P(s)C(s)}{1-P(s)C(s)}

G_{re}(s) = \frac{F(s)}{1-P(s)C(s)}

G_{re}(s) = \frac{P(s)C(s)}{1+P(s)C(s)}

G_{re}(s) = \frac{F(s)P(s)C(s)}{1+P(s)C(s)}

G_{re}(s) = \frac{F(s)}{1+P(s)C(s)}

G_{re}(s) = \frac{1}{1+P(s)C(s)}

G_{re}(s) = \frac{P(s)C(s)}{1-P(s)C(s)}

C only.

All of A, B, and C.

A and C only.

A and B only.

An unmeasured output of the plant.

An input to the plant that does not influence the output.

None of the other answers are correct.

An input to the controller.

An input to the plant that influences the output.