Looking at the function h(t), it is a polynomial function.
The domain of this type of function usually is all real numbers.
But in this case, since the independent variable t represents the time, its value can't be negative, it usually starts at t = 0.
Therefore the appropriate domain for this situation is all non-negative numbers:
[tex]\begin{gathered} t\geq0\\ \\ or\\ \\ \text{ }[0,\infty) \end{gathered}[/tex]