The answer of quizzes

The quizes

The seventh quiz

8 pieces, of course. If you watch the image to confirm it, some targets may disappear.

The sixth quiz

The rightmost reddish one. It is actually gray.

The fifth quiz

Q1 (1)

Q2 (3)

Q3 (1)

Q4 (1)

Q5 (1)

Q6 (3)

Q7 (3)

Q8 (1)

Q9 (3)

Q10 (1)

The fourth quiz

The upper one. This is the Poggendorff illusion.

The third quiz

The sixth from the left and the seventh from the top.

The second quiz

Squares c and d are the same.

The first quiz

A and C are not used. The color within each rectangle is B.