What is an isolated system?

Can any system possess thermal energy?

How is thermal equilibrium achieved in a system?

Discuss the modes (or methods) for changing the internal energy of any system.

Given are statements for certain thermodynamic variables:
$(A)$ Internal energy,volume $(V)$ and mass $(M)$ are extensive variables.
$(B)$ Pressure $(P)$,temperature $(T)$ and density $(\rho)$ are intensive variables.
$(C)$ Volume $(V)$,temperature $(T)$ and density $(\rho)$ are intensive variables.
$(D)$ Mass $(M)$,temperature $(T)$ and internal energy are extensive variables.
Choose the correct answer from the points given below:

Describe an experiment that illustrates the modern concept of heat as a form of energy and how work can be converted into heat.