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)//2`
B. `I_(0)//4`
C. `I_(0)//8`
D. `I_(0)`