What happens when an electrical gradient and a chemical gradient are applying opposite forces to active transport?

In a cell, there are two kinds of gradients found, that is, chemical and electrical. The electrical gradient is produced by the net charge of negative and positive charges found across the membrane. The chemical gradient is produced by the concentration of ions across the membrane. In combination, it is called the electrochemical gradient, which in general function in reverse directions.  

The procedure where pumping of ions takes place across the membrane via ion pumps against the electrochemical gradient is known as the active transport. This mode of transport sustains the balance of ions across the membranes and is dependent upon energy. The ATP is provided by the metabolic activities of the cell.  

the darker peppered moth species were favored due to the fact that the industrial revolution had made all the nearby trees a darker color instead of white.

i think the answer is b.