Answer:
It is the root source of energy the "life blood" of the stars.
Explanation:
It's the stimulus because that's what triggers the salivation which is the reaction
The two types of limiting factors are Density - dependent and Density independence. <span> Density-dependent limiting determinants depends on the community size; the comprehensive population, the consequential influence a density-dependent limiting agent will ought. Density-independent limiting determinant does not really depend on inhabitants dimension, alternatively they change all populations proportionately. </span>
I think the system you are referring to is the muscular system
