Requirement of special membrane proteins
High selectivity
Transport saturation
Uphill transport
Facilitated transport is the process of spontaneous passive transport or downhill transport of molecules or ions across a biological membrane via specific transmembrane integral proteins. The movement of molecules or ions is from a region of higher concentration to a region of lower concentration. Uphill transport, on the other hand, requires energy and moves molecules against their concentration gradient. Thus, the correct answer is option (D), 'Uphill transport'.