How does the concept of action- reaction apply to the human body?

The physical body of human work accosting to Action-Reaction law.

Explanation:

The rule of action-reaction state that an equivalent and reverse reaction occurs with any action.  If one entity imposes force on a second entity, the second responds by exerting an equivalent force on first entity in the same direction. 

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.

i think it's letter a.