Which of the systems having following transfer functions is stable?
A
$$\frac{1}{{{{\text{s}}^2} + 2}}$$
B
$$\frac{1}{{{{\text{s}}^2} - 2{\text{s}} + 3}}$$
C
$$\frac{1}{{{{\text{s}}^2} + 2{\text{s}} + 2}}$$
D
$$\frac{{{\text{exp}}\left( { - 20{\text{s}}} \right)}}{{{{\text{s}}^2} + 2{\text{s}} - 1}}$$
Correct Answer: $$\frac{1}{{{{\text{s}}^2} + 2{\text{s}} + 2}}$$
