The word facilitate means ""to make easier."" means that the transport protein makes it easier for a molecule that cannot directly cross the cell membrane to enter or exit a cell.

Answer :FACILITATED DIFFUSIION

Explanation;Generally polar molecules like  glucose, amino acids and Ions such as potassium and sodium  can not  enter or leave  the cell  through the phospholipid bilayer membrane of the cell.  They  are assisted to pass  accross this barrier with the  help of (1) channel proteins 2) carrier proteins.

The process by which these proteins created hydrophilic (water loving environments) to carry out transport of the above molecules and ions accross the hydrophobic (water hating environment) phospholipid membrane layer  to reach the cytoplasm of cells  is called facilitated diffusion.

This transport process is not active transport, because  the moleucules moved down their concentration gradients.

Water- filled pores made up Channel proteins. They  allows charged ions to pass through, therefore Ion channels are example of channel proteins;  for example Potassium channels, Calcium channels. They are gated, thus  the protein parts can move back and front like a gate to close or open the  pores like a Gate. Channels proteins are fixed.

Carrier proteins are  flexible and change the shapes with respect to the direction to convey the molecules accross the membrane, they are not fixed.

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b. lithosphere, asthenosphere, mesosphere   is the answer most likely