What was the foreign policy that america followed at the beginning of world war i? what
did this lead to and why?

America followed a neutral policy and was convinced that United States must stay away from the internal conflicts of Europe.

However, this stance weakened the European nations such as United Kingdom, France, Belgium agains the central powers. Without proper military and geopolitical support from the USA, the allies found it difficult to defeat the Germans, Austrians and the ottomans.

Explanation:

in mcculloch v. maryland (1819) the supreme court ruled that congress had implied powers under the necessary and proper clause of article i, section 8 of the constitution to create the second bank of the united states and that the state of maryland lacked the power to tax the bank.

gibbons v. ogden, (1824), was a landmark decision in which the supreme court of the united states held that the power to regulate interstate commerce, granted to congress by the commerce clause of the united states constitution, encompassed the power to regulate navigation.

the option which was not a function of missionaries in the northwest was the first one - they established posts for trading furs and other goods.

missionaries were sent around the world to spread religion and their knowledge and others - they were not merchants who sold furs and other goods.