Final answer:
Explosive power is the key component of sprinting on a flat surface after standing for 3-5 seconds.
Step-by-step explanation:
The key component of sprinting on a flat surface after standing for 3-5 seconds is explosive power. When a sprinter propels forward after standing still, they require a burst of power and force to accelerate quickly. This explosive power allows them to generate the necessary force to start sprinting at maximum speed.