Final answer:
The trajectory of a ball thrown at a 55° angle above the horizontal across level ground is influenced by both the horizontal and vertical components of its motion.
Step-by-step explanation:
When a ball is thrown at a 55° angle above the horizontal across level ground, its trajectory is influenced by the force of gravity. The ball will follow a curved path known as projectile motion. This motion can be divided into two components: the horizontal motion and the vertical motion.The horizontal motion is influenced by the initial velocity of the ball and does not change due to the force of gravity. The vertical motion is affected by both the initial velocity and the force of gravity. The ball will reach its maximum height at the midpoint of its trajectory before falling back to the ground.Therefore, the correct answer to the given question is d) Slope.