Active transport is the movement of molecules or substance from a region of lower concentration to a region of higher concentration across a cell membrane against the concentration gradient.
Active transport requires cellular energy and are of two types:
primary active transport that uses adenosine triphosphate (ATP), and secondary active transport that uses an electrochemical gradient.
Active transport helps in the uptake of glucose in the intestines.
Cotransport or secondary active transport is the movement of molecules across a membrane it uses electrochemical potential difference that is created by pumping ions in or out of the cell.
Cotransport helps in the transport of glucose across the cell membrane.
To my opinion the answer is C. Water is an accessible and maintainable resource in the majority of the world. I say this because its definitely not A, or D. It could possibly be B but C gives more information on why so many of the sustainable energy options are water solutions. Hope this helps and that you get the question correct, God bless!
