Answer:
B cellular respiration
Step-by-step explanation:
As mentioned in the question, While running a race, a person's muscles need a constant supply of ATP. This clearly indicate that question is not about a plant but about a human being. Now let us look at the available options:
A) Photosynthesis:
The process of photosynthesis takes place in green plants which is a source for the preparation of glucose or food for them. Moreover, plants just like animals also depend on the process of respiration for the generation of energy in the form of ATP. Therefore, photosynthesis cannot be the right option.
C) Calvin cycle:
Calvin cycle is the process that is also called as dark reaction of photosynthesis. It is second step of photosynthesis which takes place during night when CO2 is used for the preparation of glucose-. Since Calvin cycle is part of photosynthesis, it takes place only in plants and not in humans.
B) Cellular respiration:
Cellular respiration is the key process in which food we eat is broken down through series of reactions to produce energy in the form of ATP. When we do exercise or run fast, our body needs a rapid input of energy to meet the body's energy demands at that moment. Therefore, the rate of cellular respiration increases. This makes cellular respiration right option.
Hope it help!