To find the height at which the tennis ball is hit, we need to evaluate the function \( h(t) \) at \( t = 0 \). The equation modeling the height of the tennis ball is:
\[ h(t) = -16t^2 + 25t + 4 \]
Substituting \( t = 0 \):
\[ h(0) = -16(0)^2 + 25(0) + 4 = 0 + 0 + 4 = 4 \text{ feet} \]
Therefore, the tennis ball is hit at a height of 4 feet.