Final answer:
The initial velocity of the projectile cannot be determined from the given information; additional data such as time of flight or horizontal distance is required to solve for the initial horizontal velocity in projectile motion.
Step-by-step explanation:
The initial velocity of a projectile fired horizontally from a height of 20 meters cannot be determined without additional information such as the time taken to hit the ground or the horizontal distance traveled. However, the problem typically seeks to evaluate the student's understanding of projectile motion, specifically the independence of horizontal and vertical motions. The provided answer choices, in this case, do not give enough information to solve the problem.
If we were given the time it takes for the projectile to hit the ground, we could use the formula for the vertical motion under gravity to find the time and then calculate the horizontal velocity (initial velocity) using the horizontal distance formula. But with no time or horizontal distance provided, we cannot determine the initial velocity just based on the height of 20 meters.