Whether the system is in an equilibrium state depends on what?

According to the zeroth law of thermodynamics,the physical quantity which is the same for two bodies in thermal equilibrium is

Why is work an extensive quantity?

The following three objects $(1)$ a metal tray,$(2)$ a block of wood,and $(3)$ a woolen cap are left in a closed room overnight. Next day,the temperature of each is recorded as $T_1, T_2$,and $T_3$,respectively. The likely situation is:

Can any system possess heat?

What are the characteristics of thermal equilibrium between two systems?