If $$ L \left\{ f(t) \right\} = F (s),$$ then the value of $$ L \left\{ e^{-at} f(t) \right\} $$ is

A

$$ F (s - a) $$

B

$$ F (s + a) $$

C

$$ F (s) $$

D

$$ F (e^as) $$