Final answer:
The velocity of the particle is never equal to zero in the given scenario.
Step-by-step explanation:
The velocity of the particle can be determined by taking the derivative of the position function. In this case, the position function is x(t) = 3t^3 + 5t. Taking the derivative, we get v(t) = 9t^2 + 5.
To find the time at which the velocity is zero, we set v(t) = 0 and solve for t. 9t^2 + 5 = 0. This equation has no real solutions, which means the velocity of the particle is never equal to zero. Therefore, none of the given options are correct or reasonable.