A beam of unpolarised light of intensity `I_0` is passed through a polaroidA and then through another polaroid B which is oriented so that its principal plane makes an angle of `45^circ` relative to that of A. The intensity of the emergent light is
A. `I_0`
B. `(I_0)/(2)`
C. `(I_0)/(4)`
D. `(I_0)/(8)`