How Does the NCKX System Differ from the NCX System

How does the NCKX system differ from the NCX system?

A) The NCX system is only expressed in the outer segment of vertebrate retinal rod cells.
B) The NCKX system is only expressed in muscle fibers.
C) The NCKX system is expressed in the plasma cell membrane, whereas the NCX system is expressed in the sarcoplasmic and endoplasmic reticulum and in mitochondria.
D) In addition to transporting sodium and calcium, NCKX transports potassium.
E) The NCKX system is a primary active transport mechanism, whereas the NCX system is a secondary active transport mechanism.