Unsteady politics in foreign countries
The majority of American intervention in the foreign affairs occurred during the Cold War (this is your answer). Latin America was a frequent hotspot for activity as well especially towards the latter half of the Cold War with Fidel Castro's rise to power in Cuba.
The only option that is not generally a reason why historians study societal change would be "<span>d. to estimate how long it would take to build a road system," since this requires a separate type of research. </span>
Answer:
<u><em>They protected the home country’s economy at the colonists’ expense</em></u>.
Explanation:
Interestingly this colonist where affected after the Wool Act because it resulted in higher value of British clothes as a result of export ban of foreign wool.
The Iron Act which was meant to increase local iron production was opposed because they were resulting in losses for the growing iron and steel companies.