If a transport protein moves two solutes across a membrane in opposite directions, the protein is called a countertransporter or

Exchanger or antiporter

Explanation:

The cotransporters are transmembrane proteins that are part of the active transport. These proteins couple the movement of a molecule or ion against its concentration gradient with the movement of one or more cotransporter ions under its concentration gradient, thus allowing the passage of large molecules such as glucose into the cell that transport Passive would not be possible to enter. There are two types:

Simporters:

They are transmembrane molecules that involve the movement of two or more different ions through the phospholipid membrane of the membrane in the same direction. Generally the ions move under the electrochemical gradient allowing the other molecule to move against the concentration gradient.

Exchanger or antiporter (countertransporter):

They are transmembrane molecules that involve the movement of two or more different ions through the phospholipid membrane in opposite directions, where one species of the solute moves in favor of the electrochemical gradient, allowing the other species a movement against their gradient of concentration

c should be the answer