The process of involves a carrier protein that can transport a molecule across the cell membrane down its concentration gradient. the process of involves a carrier protein that can transport a molecule across the cell membrane down its concentration gradient. bulk transport facilitated diffusion osmosis active transport simple diffusion

Molecules such as glucose and amino acids can be absorbed from the digestive tract and a renal tubule by the process of facilitated diffusion, which involves a carrier protein that can transport a molecule across the cell membrane down its concentration gradient. The process involves a process of spontaneous passive transport of molecules or ions across a biological membrane via specific trans-membrane integral proteins. 

The correct answer is b