Answer
Choice B.
Work Step by Step
In case 1, the first two polarizers have perpendicular transmission axes, and in case 3, the last two polarizers have perpendicular transmission axes. No light gets through in cases 1 or in case 3.
Case 2 is similar to Example 24-14 (Figure 24-45). No two adjacent polarizers have their axes perpendicular to each other, so some light can get through.