At the highest point of its trajectory, an oblique projectile's vertical velocity is zero. However, it still retains its horizontal velocity. Therefore, the direction of the oblique projectile at its highest point is horizontal.

Here's why:

* Vertical motion: Gravity acts on the projectile, slowing its upward motion until it momentarily stops at the peak.

* Horizontal motion: In the absence of air resistance, there is no force acting horizontally. So, the horizontal velocity remains constant throughout the projectile's flight.

Think of it like throwing a ball upwards. As it reaches its peak, it stops moving upwards for a brief moment before falling back down. But it's still moving forward in the direction you threw it.