The correct answer is: D. density of mercury is more than the water.
Mercury is commonly used as a thermometric fluid rather than water because it has a higher density than water. This means that mercury will expand and contract more than water when heated or cooled, which makes it a more accurate way to measure temperature. Additionally, mercury is a non-polar liquid, which means that it does not form hydrogen bonds with other molecules. This makes it less likely to stick to the sides of the thermometer, which can also affect the accuracy of the reading.
The specific heat of mercury is actually more than water. This means that it takes more energy to raise the temperature of mercury by one degree Celsius than it does to raise the temperature of water by one degree Celsius. This is not a desirable property for a thermometric fluid, as it would make the thermometer more difficult to use.
Mercury has greater visibility than water, but this is not a major factor in its selection as a thermometric fluid. The main reason for using mercury is its high density.
Therefore, the correct answer is: D. density of mercury is more than the water.