To find the time at which the volleyball reaches its maximum height, we can use the vertex formula for a quadratic function, given by the equation \( h = -16t^2 + 33t + 6 \). The vertex of a parabolic equation in the form \( h(t) = at^2 + bt + c \) occurs at \( t = -\frac{b}{2a} \).
Here, \( a = -16 \) and \( b = 33 \).
Let's calculate the time \( t \):
\[ t = -\frac{b}{2a} = -\frac{33}{2 \times -16} = \frac{33}{32} \approx 1.03 \text{ seconds} \]
So, the volleyball reaches its maximum height at approximately 1.03 seconds.
Therefore, the domain of the ball when it reaches its maximum height is up to about 1.03 seconds. The valid response based on the available options is:
1.03 seconds.