Answer: The correct answer is option A.
Explanation:
Facilitated transport is a type of passive transport in which movement of molecules is done with the help of integral membrane protein or carrier protein. It can also be called as transporter protein. They form channels or carrier in the membrane.
Being passive in nature, the transport does not include the expenditure of energy (ATP) rather it is done down the concentration gradient.
It is used when the molecule is big in size or when a molecule can not pass from hydrophobic core of the plasma membrane such as charged or polar molecules.
For example, glucose transport through GLUT 4, carrier proteins for gases such as oxygen, carbon monoxide, carbon dioxide, et cetera.
