Final answer:
The transporter becomes saturated with K+ ions, slowing down the rate of transportation.
Step-by-step explanation:
When the concentration of K+ ions is increased outside a nerve cell, it affects the rate of transportation through a transporter. The correct answer is A) The transporter becomes saturated with K+ ions, slowing down the rate of transportation. There are a finite number of carrier proteins in the membrane, and when all of them are bound to K+ ions, they are saturated. Increasing the concentration gradient at this point will not result in an increased rate of transport.