The Laplace transform of exp(at), where a > 0, is defined only for the Laplace parameter, s > a since______________?

A. The function is exponential
B. The Laplace transform of integral of exp(at) has finite values only for s > a
C. The Laplace transform integral of exp(at) has initial values only for s > a
D. The function exp(at) is piece-wise continuous only for s > a