The correct answer is C) Because they might have to fight foreign threats.
A provisional government be needed in Oregon because they might have to fight foreign threats.
The provisional government was created in 1843 by non-natives that inhabited those territories of the Pacific Coast. These people wanted to respect the rule of law in Oregon. In those years, both the British and the Americans were very interested in the Oregon region, although the London Convention treaty did not allow them any kind of power to occupy those territories. That is why the non-native setters decided to establish its provisional government.