Final answer:
The range of a projectile is zero when it is launched at a 90° angle, straight up, or at a 0° angle, straight horizontally. Hence, the correct answer is c. 90° or 0°.
Step-by-step explanation:
The range of a projectile is the horizontal distance it travels while in motion. When considering angles for maximum range, one must take into account the principles of projectile motion. The question involves the angle at which the range of the projectile would be zero.
A projectile's range will be zero when it is launched vertically upwards, because in this scenario, it will simply go up and then come back down to the same spot it was launched from. Therefore, the angle which results in zero horizontal range is when the projectile is launched at a 90° angle. When launched at 0°, the projectile moves horizontally, but since the initial vertical velocity component is zero, it does not cover any vertical distance, and hence, it touches the ground immediately, technically resulting in a zero range as well.
Based on the given options, the correct answer to the question 'For what angle of a projectile is its range equal to zero?' is c. 90° or 0°.