Attorney General Robert Kennedy wanted to end the Freedom Rides, seeking

a.

to avoid alienating white southern voters.

b.

a "cooling-off period."

c.

another racial riot in the Watts section of Los Angeles.

d.

more legislation.

B. A "cooling-off period."

Explanation:

The Freedom Rides, was a movement initiated by a group consisting of twelve African-Americans and six whites, who were commemorating the seventh anniversary of a decision of the Supreme court which ruled that segregation in schools across the country was not constitutional. These groups attempted entering 'whites only' areas and this action, resulted in violent attacks by white mobs. The movement began on May 4, 1961.

When the situation became really critical, Attorney General Robert Kennedy, issued a statement where he advised that a cooling-off period be observed until a state of normalcy is restored. He reasoned that some of the travelers in the buses were innocent people who needed to get to their destinations, and so could easily be attacked by the mob who asks no questions.  

the monroe doctrine is the best known u.s. policy toward the western hemisphere. buried in a routine annual message delivered to congress by president james monroe in december 1823, the doctrine warns european nations that the united states would not tolerate further colonization or puppet monarchs.