To find \((f \circ g)(t)\), we need to substitute \(g(t)\) into \(f(d)\).
The function \(g(t)\) is given by: \[ g(t) = 6t. \] The function \(f(d)\) is given by: \[ f(d) = \sqrt{49 + d^2}. \]
Now we substitute \(g(t)\) into \(f(d)\): \[ (f \circ g)(t) = f(g(t)) = f(6t) = \sqrt{49 + (6t)^2} = \sqrt{49 + 36t^2}. \]
This means that \((f \circ g)(t)\) represents the distance the wave runner is from the dock after \(t\) hours.
Now, let's determine the domain of \((f \circ g)(t)\).
Since \(t\) represents the time in hours that the wave runner has traveled, it is restricted to non-negative values: \[ t \geq 0 \] because time cannot be negative.
Thus, the domain of \((f \circ g)(t)\) is: \[ [0, \infty) \]
Now, we can match this to the provided multiple choice responses. The correct response should be:
\((f\circ g)(t)=\sqrt{49+36t^2}\) represents the distance the wave runner is from the dock after \(t\) hours. The domain is \(t \geq 0\).