What is called absolute zero temperature?

Mercury is often used in clinical thermometers. Which one of the following properties of mercury is not a reason for this?

On which of the following temperature scales is the temperature never negative?

$A$ new temperature scale uses $X$ as a unit of temperature,where the numerical value of the temperature $t_x$ in this scale is related to the absolute temperature $T$ by $t_x = 3T + 100$. If the specific heat of a material using this unit is $1400 \, J \, kg^{-1} X^{-1}$,its specific heat in the $SI$ system of units is:

$A$ constant pressure air thermometer gave a reading of $47.5$ units of volume when immersed in ice cold water, and $67$ units in a boiling liquid. The boiling point of the liquid will be .......... $^\circ C$.

Write the relation between Celsius and Fahrenheit scales with a graph.