The option that most effectively completes the sentence is “allowing world nations freedom of choice, within reason, promotes peace”. According to John Kennedy in his speech delivered at the American University, nations (in this case he refers to the Soviet Union) should not try to impose rules on other nations as this interferes with the process of peace and creates tension.
In texting we would (normally) not use proper grammar, but when we’re writing we normally use proper grammar sense someone important is more likely to read it
Sentence A has a disagreement between "were" (plural) and "no one" (singular).
Sentence B has a disagreement between "was" (singular) and "problems" (plural).
Sentence C, however, has complete agreement between the subject and verb. Therefore, the answer is C.
