Why we say that the cell is a complex system

Mostly because they can function independently. For example, microorganisms, more especifically unicellular organisms, are composed by one cell, meaning they're a cell, but even so can function like a normal living organism.

Hope it helped,

BioTeacher101

i might be wrong but i think its a. let me know if i’m right and have a good rest of your day!

in a chemical reaction, the atoms and molecules produced by the reaction are called products. no new atoms are created, and no atoms are destroyed. in a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.