In this case, the function \( n(t) = 50(1.2)^t \) represents the number of bacteria after \( t \) hours. The variable \( t \) represents time, measured in hours, and since time cannot be negative in this context, the appropriate domain for \( t \) would be non-negative values.
Thus, the appropriate domain for the function \( n(t) \) would be:
\[ t \geq 0 \]
In interval notation, this can be expressed as:
\[ [0, \infty) \]
This means that the scientist can observe the population starting from time \( t = 0 \) (the initial population) and continuing for as long as needed (including the 4-hour mark).