Which of the curves in the figure represents the relation between Celsius and Fahrenheit temperatures?

The graph $AB$ shown in the figure is a plot of the temperature of a body in degree Celsius $(C)$ versus degree Fahrenheit $(F)$. Then:

Explain the study of thermal properties of matter by giving definitions of temperature and heat.

''Amount of heat is greater in hot body than cold body.'' Check the correctness of this statement.

What is the change in temperature on the Fahrenheit scale and Kelvin scale,if an iron piece is heated from $30\ ^oC$ to $90\ ^oC$?

$A$ 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: