Which of the following is a word without an English suffix

A．to investigate threats to security of the United States that take place within the U.S. borders
B．to stop the spread of communism in Central and South America
C．to protect the president and vice-president
D．to coordinate intelligence operations

A．Invading Britain.
B．Being assassinated while attending session of the Roman Senate.
C．Persecuting Christians.
D．Establishing the 365-day calendar.