Which of the following conditions is most favorable for the liquefaction of a gas?

What is the value of the critical temperature of water (in $K$)?

The compressibility factor $(Z)$ of a gas at critical state is $(T_c = \frac{8 a}{27 R b}; p_c = \frac{a}{27 b^2}; V_c = 3 b)$.

At what point does surface tension vanish?

The isotherms of a gas are shown below:
Among the following:
$(i)$ At $T_1$,the gas cannot be liquefied.
$(ii)$ At point $B$,liquid starts to appear at $T_2$.
$(iii)$ $T_c$ is the highest temperature at which the gas can be liquefied.
$(iv)$ At point $A$,a small increase in pressure condenses the whole system to a liquid.
The correct statements are:

What is the surface tension at the critical temperature?