After reading the passage attached, we can choose the following detail to support Nixon's primary claim:
A. "but the interest of the nation must always come before any personal consideration." (paragraph 4)
Nixon's purpose in the speech is to resign office, that is, to stop being president of the United States.
He claims that he is only doing what is best for the country, that he is not thinking of himself.
The detail that supports that claim is found in paragraph 4, "but the interest of the nation must always come before any personal consideration."
What Nixon means is that, even if his wishes are different, he must consider what the nation needs. Since he does not have support from the Congress, he must leave office.
With that in mind, we can choose letter A as the best option.
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