Acell is in when solute concentrations inside and outside the cell are equal.

equilibrium                is the answer

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme

it's not c. i took the quiz and got it wrong. so my best guess is b.

have a great day, and hope this .