Darkhold. A student writes down the electric field and magnetic field of an electromagnetic wave as E = Eo cos(ka + wt) B = Bo cos(ka + wt) but forgot to write down the directions. Which of the following electric and magnetic field directions would result to a correct EM wave? (Assume that Eo > 0 and Bo > 0) O A. E to the + y-direction ; B to the + z-direction O B. E to the +x-direction ; B to the + z-direction O C. E to the + z-direction ; B to the +x-direction O D. E to the + 2-direction ; B to the +y-direction