The second president of the United States was

John Adams was the second president of the United States serving from 1797 to 1801. He was also a founding father and played an important role in the American Revolution. Before becoming president he served as the first vice president under George Washington. His presidency was marked by challenges such as conflicts with France and domestic political divisions. Adams was a strong supporter of independence and diplomacy. Though he lost re election to Thomas Jefferson he is remembered for his contributions to the foundation of the United States. Hence the correct answer is option C John Adams.