what is the purpose of the phrase "secure the blessing of liberty to ourselves and our posterity" in the preamble to the U.S. constitution

O A. To state that the government is expected to protect American freedoms

O B. To guarantee that the U.S. government will have separation of powers

O C. To place strict limits on the power of the U.S. federal government

O D. To show that the people hold all political power in the country