The Decay Factor of an Exponential Function $P ( t )$

Multiple Choice

The decay factor of an exponential function $P ( t )$ is 0.68. The initial value is 1.45. Then a formula for P is

A) $\rho = 0.68 \times t ^ { 1.45 }$
B) $P = 0.68 \times 1.45 ^ {t }$
C) $P = 1.45 \times t ^ { 0.68 }$
D) $P = 1.45 \times 0.68 ^ { t }$