Which of the substances $A, B$ or $C$ has the highest specific heat $?$ The temperature vs time graph is shown

A solid material is supplied with heat at constant rate and the temperature of the material changes as shown below. From the graph, the false conclusion drawn is:

Answer the following questions based on the $P$ - $T$ phase diagram of carbon dioxide:

$(a)$ At what temperature and pressure can the solid, liquid and vapour phases of $CO _{2}$ co-exist in equilibrium?

$(b)$ What is the effect of decrease of pressure on the fusion and boiling point of $CO _{2} ?$

$(c)$ What are the critical temperature and pressure for $CO _{2} ?$ What is their sıgnificance ?

$(d)$ Is $CO _{2}$ solid, liquid or gas at $(a)\;-70\,^{\circ} C$ under $1\; atm$, $( b )\;-60\,^{\circ} C$ under $10 \;atm,$ $(c)$ $15\,^{\circ} C$ under $56$ atm ?

The portion $A B$ of the curve representing the state of matter denotes

$Assertion :$ Melting of solid causes no change in internal energy.
$Reason :$ Latent heat is the heat required to melt a unit mass of solid.

What is the effect of pressures on boiling point of water ?