the formula a(t)=12,000e^(0.04)t models the growth of an investment due to continuously compounded interest…

Brief Explanations:

In the continuous - compounding interest formula $A(t)=P e^{rt}$, where $A(t)$ is the amount of money after $t$ years, $P$ is the principal (initial amount), $r$ is the annual interest rate, and $t$ represents the number of years since the initial investment. Here, $12000$ is the initial amount $P$, $0.04$ is the interest rate $r$, and $t$ is the time in years.

Answer:

A. the number of years since the initial investment