Final answer:
During intense activities such as weightlifting where oxygen is scarce, muscles utilize lactic acid fermentation to produce energy.
Step-by-step explanation:
The production of lactic acid is most likely to occur during activities that require a high demand for energy in a short period, where the oxygen supply to the muscles is inadequate to meet the energy needs through aerobic respiration. Considering the options provided, weightlifting is the activity during which the production of lactic acid is most likely to occur. This is because weightlifting is an intense activity that involves exerting muscles to the point of fatigue, leading to a situation where the muscle cells switch to lactic acid fermentation for energy.
Lactic acid fermentation occurs routinely in mammalian red blood cells and in skeletal muscle cells under conditions of low oxygen availability, which is common during strenuous activities. This anaerobic pathway converts pyruvic acid and NADH into lactic acid and NAD+, helping to sustain muscle activity when oxygen is scarce.