Final answer:
Supplementary deflection indexes indicate a secondary aiming point. It is a term from artillery for adjusting aim due to various factors. The concept relates to adjusting for angles and directions in artillery, similar to how vectors are directed in physics or bearings in navigation.
Step-by-step explanation:
Supplementary deflection indexes indicate a B) Secondary aiming point. This term is typically associated with artillery and similar subjects where one must adjust aim for factors like wind or elevation. Deflection in artillery terms refers to the lateral adjustment of the aiming point to compensate for factors such as wind, rotation of the earth, or the movement of the target. Supplementary deflection is an additional aiming point used when the primary aiming point is unsuitable for direct fire due to various conditions or obstructions.
The direction of a vector in physics can be indicated with various methods, including supplementary angles, while in navigation, one might refer to bearings or compass directions such as 'N 30° W'. These concepts are related to the accuracy of calculation in artillery or when considering the zenith angles in astronomic observations.
Projectile range is related to the launch angle, where a projectile with a range of zero would have an angle of c. 90° or 0°, since at 90° the projectile would go straight up and come down the same place, while at 0° it wouldn't cover any horizontal distance as it would be launched parallel to the ground.