Web diagram with circles and arrows. There are four circles along the top row and two circles on the bottom row. Going from left to right, the top left circle contains the letter "A" with a question mark. The second circle contains the word "Solids." The third circle contains the letter "B" with a question mark. The fourth circle contains the word "Gases." On the bottom row, the circle on the left contains the word "Metals" and the circle on the right contains the letter "C" with a question mark.