A hypothetical ion (B+) is in high concentration on one side of a membrane and low concentration on the other side. At first, no B+ can cross the membrane, but then several B+ ion channels open and B+ starts crossing the membrane. As they cross, an electrical gradient begins to form. After a while, the electrical gradient, and the B+ concentration gradients equalise in strength. Which of the following statements is true at the time the electric and concentration gradients have equalised? a) The B+ concentration is LOW where the electric charge is negative. B) The concentration gradient cancels out the electrical gradient, so the membrane potential is 0mV. C) The B+ concentration is the same on both sides of the membrane (no concentration gradient across the membrane). D) The B+ concentration is HIGH where the electric charge is negative.