There are 24 different complex numbers z such that z24=1. For how many of these is z6 a real number?<spanclass=′latex−bold′>(A)</span>1<spanclass=′latex−bold′>(B)</span>3<spanclass=′latex−bold′>(C)</span>6<spanclass=′latex−bold′>(D)</span>12<spanclass=′latex−bold′>(E)</span>24