Answer:
b. The light waves are completely blocked.
Step-by-step explanation:
When light incident on first polarizer then intensity of light becomes half of its initial intensity after passing through it.
It is because oscillation of light is confined into one plane and light becomes polarized after passing through it
Now another polarizer is placed in front of it at some angle then as per Malus law the intensity of light after passing through that is given by

here we know that
= angle between the axis of analyser and polariser axis
here given that analyser and polariser are inclined at 90 degree with each other
so intensity of light received after passing analyser is

so correct answer will be
b. The light waves are completely blocked.