The internal energy of a system is always increased bya)adding heat to the system and having the system do work on the surroundings. b)having the system do work on the surroundings. c)withdrawing heat from thesystem. d)adding heat to the system. e)a volume decompression.

A)adding heat to the system and having the system do work on the surroundings

Explanation:

The variation in the internal energy of a system (ΔU) is given by the First Law of Thermodynamics. See the equation below:

ΔU = Q + W

Q: Heat added (+) or removed (-) from the system

W: work done on (-)  or done by (+) the system

If you add heat (Q +) and have the system do work (W +), you guarantee that th internal energy of the system will increase (ΔU +).

c.

explanation:

gas

explanation:

smoke is the matter of a gas