Three identical photocells are illuminated separately by monochromatic beams of the same frequency (ν>ν0) but with intensities I1=0.5I0, I2=I0 and I3=2I0. Which of the following correctly arranges the corresponding saturation currents (I1s, I2s, I3s) in ascending order?
a) I1s=I2s=I3s
b) I3s<I2s<I1s
c) I1s<I2s<I3s
d) I2s<I1s<I3s