Final answer:
The optimum angle at which a projectile should be launched to cover the maximum distance is 45°.
Step-by-step explanation:
The range of a projectile is the horizontal distance it travels before reaching the ground. The angle at which a projectile should be launched to cover the maximum distance is called the optimum launch angle. According to the given options, the optimum launch angle to cover the maximum distance is 45° (option b).