The most significant cause of the trend from 1755-1762 shown in the table would be:
(Choice C) costs of involvement in the Seven Years’ War with France.
The Seven Years' War (1756-1763), known in North America as the French and Indian War, was a major conflict that involved significant military expenditures and ultimately shifted the balance of power in colonial territories. The financial burden of the war and its aftermath had lasting effects on British colonial policy and finance.