This diagram was constructed according to a certain logic. Can you work out which number should replace the question mark?

4

Step-by-step explanation:

I'm guessing that each number represents the number of rectangles that overlap. Where you see 1, there is only one rectangle, 2 shows where two rectangles overlap, and so on.

At the question mark, it appears as though four rectangles overlap. So a 4 would go there.

1. d.90

2. e. none of these (80)

3. a. 0

4. b. 6

5. e. none of these (10)

6. a. 5