Which of the following is a true statement about a projectile's acceleration during its flight in a vacuum?

It remains constant at g downwards. In a vacuum, the acceleration of a projectile during its flight remains constant at g, which is the acceleration due to gravity. This value is approximately 9.8 m/s^2 downwards on Earth's surface. Regardless of the object's initial velocity and launch angle, gravity constantly acts on the object, pulling it downwards at a consistent rate. This constant acceleration is what gives the trajectory its parabolic shape, as the object's vertical velocity changes while its horizontal velocity remains constant. At the peak of the trajectory, the object's vertical velocity momentarily becomes zero, but its acceleration due to gravity remains the same, causing it to begin its descent back to the ground.