Visual IQ puzzle (MENSA Denmark, difficulty 3)
Correct answer: F
Explanation: Each figure is a 3x3 grid that contains grey, red and blue squares. When going from left to right, a grey square gets added at each step, creating al alternated white and gray pattern of cells. There can only be 2 grey squares per figure's row. When going from left to right, the red and blue squares move by one cell to the right. When a red or blue square reaches the end, it pops up at the beginning of the row below. The gray squares can conver the colored squares. When a red tile goes under a grey tile, it becomes blue and viceversa.