For a concentration cell, the standard cell potential is always:. a. positive
b. negative
c. zero
d. need more information

C. Zero

Explanation:

A concentration cell is defined as a type of galvanic cell which has two equivalent half-cells of the same constituent in the electrodes but different concentration in the electrolytes.

For a concentration cell, the standard cell potential is always Zero and the cell potential is usually measured with the use of the Nernst equation.

the answer would be a