"To our sister republics south of our border, we offer a special pledge: to convert our good words into good deeds, in a new alliance for progress; to assist free men and free governments in casting off the chains of poverty. But this peaceful revolution of hope cannot become the prey of hostile powers. Let all our neighbors know that we shall join with them to oppose aggression or subversion anywhere in the Americas.
And let every other power know that this Hemisphere intends to remain the master of its own house."

Which sentence best explains how the bolded portion develops the author’s ideas in this paragraph?

Question

"To our sister republics south of our border, we offer a special pledge: to convert our good words into good deeds, in a new alliance for progress; to assist free men and free governments in casting off the chains of poverty. But this peaceful revolution of hope cannot become the prey of hostile powers. Let all our neighbors know that we shall join with them to oppose aggression or subversion anywhere in the Americas. 
And let every other power know that this Hemisphere intends to remain the master of its own house."

Which sentence best explains how the bolded portion develops the author’s ideas in this paragraph?