Answer:
Discrimination.
Explanation:
Jus in Bello is a part of Just War Theory, also known as Jus Bellum Justum, doctrine which suggests the just ways to fight in a war. The Jus war theory is divided into two parts, that is, jus ad bellum (which means right to go to the war) and jus in bello (right ways of conduct in the war).
The Jus in Bello theory is divided into two principles, namely, proportionality and discrimination.
The principle that bans the use of certain kinds of warfare because they are seen bad in themselves is Discrimination.
The prinicple of discrimination in jus in bello bans the use of certain weaponry that discriminate humanity. These weapons may include nuclear weapon, poisonous gas, etc.
So, the correct answer is third option, discrimination.
