In each of the following cases, initially vertically polarized light enters the polarizing apparatus with the same initial intensity. Which polarizing apparatuses will cause the light to exit with the largest intensity, 90° from its initial polarization? 
a) A single polarizing filter, oriented 90° from the vertical 
b) Two polarizing filters, the first 45° from the vertical and the second 90° from the vertical 
c) Two polarizing filters, the first 60° from the vertical and the second 90° from the vertical 
d) Two polarizing filters, the first 30° from the vertical and the second 90° from the vertical.