In 1957, the Arkansas National Guard prevented nine African American students from attending Central High School in Little Rock. In response, President Eisenhower sent in federal troops to force the school to integrate. What gave President Eisenhower the right to send in the federal troops?

A. Because Arkansas was violating federal law, the president had the right to enforce the Constitution.
B. Because Arkansas was using National Guard troops, they violated federal military restrictions.
C. Because Arkansas was allowing troops to enter a school, the president had the right to protect the students.
D. Because Arkansas did not have its own constitution, it had to follow the federal laws on constitutional rights.