Which organ system is similar to the function of a nucleus? A. Digestive system
B. Excretory system
C. Nervous system
D. Endocrine system

its the nervous system

Explanation:

because The smooth endoplasmic reticulum in the cell is similar to our endocrine system because The centriole in the cell is similar to our reproductive system

in chemistry, a solution’s concentration is how much of a dissolvable substance, known as a solute, is mixed with another substance, called the solvent. the standard formula is c = m/v, where c is the concentration, m is the mass of the solute dissolved, and v is the total volume

the answer is na (sodium)