Answer:
Anaerobic respiration.
Explanation:
Living beings used to respiration process to synthesize ATP. There are two types of respiration i. e. aerobic respiration and anaerobic respiration. in aerobic respiration, organisms synthesize ATP in the present of oxygen in very large amount while in anaerobic respiration, organisms produces ATP in the absence of oxygen but in very low concentration. So anaerobic respiration is the process used by organisms as an alternate method to produce ATP without oxygen.
