Which best defines the “stab in the back” myth?

It is the idea that Jews betrayed Germany by orchestrating its defeat in World War I.
It is the belief that the Weimar Republic would betray Germany if allowed to remain in power.
It is the idea that Germany’s allies, the Ottoman and Austro-Hungarian empires, failed them in World War I.
It is the notion that disloyal soldiers were the cause of Germany’s defeat in World War I.

Is it "It is the idea that Jews betrayed Germany by orchestrating its defeat in World War I." ?

Yes, it is A.

For the future people^^^^

Yes, you are correct. The "stab in the back" myth refers to the idea that Jews betrayed Germany by orchestrating its defeat in World War I. This false belief emerged in the years following Germany's surrender in World War I, when some right-wing politicians, military leaders, and nationalist groups sought to find a scapegoat for the country's loss. They blamed a perceived lack of loyalty within Germany itself, particularly pointing fingers at Jews, socialists, and liberals. It is important to note that the "stab in the back" theory is a baseless and anti-Semitic conspiracy theory that has been thoroughly debunked by historians.

Right

https://encyclopedia.1914-1918-online.net/article/stab-in-the-back_myth