Cells require glucose as a source of energy to carry out life processes. large molecules like glucose cross the cell's plasma membrane
a.) being pumped through ion channels
b.) active transport through protein channels
c.) passive diffusion through the lipid bilayer
d.) facilitated diffusion through protein channels

The best answer is D.

Facilitated diffusion is a transport mechanism in which carrier proteins shuttle molecules across a plasma membrane without using the cell's energy . The energy is provided by the concentration gradient i.e. molecules are transported from higher to lower concentrations, into or out of the cell.

Glucose binds to carrier proteins of the GLUT family. Once bound, the change shape so as to fit in the membrane channels and thus they translocate the glucose molecule from one side of the plasma membrane to the other.