18) which of the following best describes how chromosomes move toward the poles of the spindle during mitosis? ; a) the chromosomes are "reeled in" by the contraction of spindle microtubules.; b) motor proteins of the kinetochores move the chromosomes along the spindle microtubules.; c) nonkinetochore spindle fibers serve to push chromosomes in the direction of the poles.; d) the chromosomes are "reeled in" by the contraction of spindle microtubules, and motor proteins of the kinetochores move the chromosomes along the spindle microtubules.; e) the chromosomes are "reeled in" by the contraction of spindle microtubules, motor proteins of the kinetochores move the chromosomes along the spindle microtubules, and nonkinetochore spindle fibers serve to push chromosomes in the direction of the poles.