The transfer function of a pure dead time system with dead time $${\tau _{\text{d}}}$$ is

A. $$\frac{1}{{{\tau _{\text{d}}}{\text{s}} + 1}}$$

B. $${\tau _{\text{d}}}{\text{s}} + 1$$

C. $${{\text{e}}^{ - {\tau _{\text{d}}}{\text{s}}}}$$

D. $${{\text{e}}^{{\tau _{\text{d}}}{\text{s}}}}$$

Answer: Option C