Which of the following corresponds to the function of raising the membrane potential to the activation threshold?a.pressing the handle on a flush toilet b.stepping away from a rock after rolling it uphill c.releasing an arrow d.filling the tank on a flush toilet e.a and b f.a and c g.a and d h.b and c i.b and d j.c and d k.a, b, and c l.a, b, and d m.b, c, and d n.all of these o.none of these