ANS:B - water

In the case of most substances, including carbon dioxide, water, and mercury, the density of the solid state is higher than that of the liquid state. This means that the molecules or atoms are more closely packed together in the solid phase compared to the liquid phase. However, there is an exception, and that is water. Water is unique in that its solid form, ice, has a lower density than its liquid form. This is why ice floats on water. When water freezes, its molecules form a crystalline structure with a relatively open arrangement, leading to lower density compared to liquid water. So, the correct answer to your question is: Water