At the highest point of a projectile's motion, the vertical velocity is zero, and the acceleration is 9.8 m/s² downward (due to gravity).

Therefore, the correct answer is:

B. zero, 9.8 m/s² downward.

Explanation:

• Vertical velocity: At the highest point, the projectile momentarily stops moving upwards and starts descending, so the vertical velocity is zero at that instant.
• Acceleration: Regardless of the projectile's position, the acceleration due to gravity is always directed downward and has a magnitude of approximately 9.8 m/s² on Earth.

Would you like more details or have any further questions?

Here are 5 related questions to deepen your understanding:

1. Why is the horizontal velocity constant in projectile motion?
2. How does the angle of projection affect the range of a projectile?
3. What happens to the vertical acceleration if the projectile is launched upwards?
4. How do you calculate the maximum height of a projectile?
5. How does air resistance impact projectile motion in real-world scenarios?

Tip: Always break the motion of a projectile into horizontal and vertical components to analyze them separately for clarity.