Question

What was a major catalyst for World War I?

European countries invading each other for land.

Treaties that forced many countries to get involved if an alliance member was attacked.

Empires granting their colonies independence, leaving them to fend for themselves.

Unrest of the poor and oppression of the weak would be major issues prompting World War I

Answer 1

The best choice is:
"Treaties that forced many countries to get involved if an alliance member was attacked."

Why: the alliance (treaty) system turned a regional crisis into a world war. After Archduke Franz Ferdinand was assassinated in June 1914, Austria-Hungary’s action against Serbia triggered obligations and mobilizations among allied powers (Russia, Germany, France, Britain), producing a chain reaction of declarations of war. Long‑term causes like militarism, nationalism and imperial/colonial rivalry contributed, but the alliance system was the immediate catalyst that escalated a local conflict into World War I.