The british encouraged arab nations to revolt against the ottoman empire because the

Ottoman empire had allied itself with Germany in World War I

Explanation:

In 1915, the British needed the help of the Arabs in defeating the Ottoman Empire in World War I, they promised the Arabs that if they rebelled against The Ottoman Empire (which had sided with Germany in the war), that they would get their own independent state.

However the Arabs fought and died for the British, thinking that they would gain their independence as a reward for their sacrifice. Yet what ended up happening instead, is that the British and French marched into their territory and claimed the remains of empire for themselves.

other sources of text

explanation:

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congress also has implied powers, which derive from the necessary and proper clause of the constitution and permit congress "to make all laws which shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this constitution in the government of the united states.