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. $$\frac{{{\text{exp}}\left( { - 20{\text{s}}} \right)}}{{{{\text{s}}^2} + 2{\text{s}} - 1}}$$

Answer: Option C