Different chemical reactions are used in combinations during chemical synthesis in order to obtain a desired product. In biochemistry, a consecutive series of chemical reactions (where the product of one reaction is the reactant of the next reaction) form metabolic pathways.
AF-S is AF 'single'- your camera will focus on a fixed object when you press the AF button and will remain focused on that point for as long as you hold the button down.This is best for static subjects.AF-C is AF 'continuous' - the camera will focus on whatever is in the relevant AF points (depending on how you have your AF coverage set up) and will attempt to keep the subject in focus wherever it moves, whether that's towards/away from the camera or laterally.F-A is AF 'auto' and automatically switches between the two AF modes depending on what the subject is doing. This requires less effort on the part of the photographer, but you are relying on the camera guessing correctly what you are focussing on, and may result in unexpected focus.
Air Force and Navy are pretty comparable for being the least physically demanding. They also seem to have similar requirement for enlisting (minimum ASVAB scores). It's a bit higher than the Marines and Army but the threshold isn't huge either. So, in that regard it is rather negligible. If it comes down to simply the least rigorous training, then it would probably be between AF and Navy. Then youâd have to consider the lifestyle differences. They both PT about the same rate and have similar fitness standards. Deployment and rotation phases are a bit different though.