Final answer:
Thomas Jefferson represents both the promise and problems of the revolutionary period and America's founding due to his contradictions, including owning slaves while championing liberty. Therefore, the correct option is C.
Step-by-step explanation:
Thomas Jefferson represents both the promise and problems of the revolutionary period and America's founding due to his contradictions, including owning slaves while championing liberty. Although he played a significant role in writing the Declaration of Independence and advocated for slavery abolition in theory, he owned over 200 slaves during his lifetime and only freed a small number of them. This contradiction highlights the complex issues surrounding slavery during that time.