The three cases of personal pronouns are objective, possessive, and nominative.
I, we, you, he, she, it, they are nominative cases. They are used when a personal pronoun is used as the subject of a verb or as a predicate nominative.
Me, us, you, him, her, hers, its, their, and theirs are objective cases. They are used when the noun or pronoun is used as an direct or indirect object of a verb, or as the object of a preposition.
My, mine, our, ours, your, yours, his, her, hers, its, their, theirs are possessive cases. They are used to show ownership.
The correct answer is B. President Truman was under intense pressure from the very beginning of his term of office.
Explanation
The excerpt begins with the subject of President Truman's decision to drop the atomic bomb. However, he later expands on this issue by arguing that after suddenly assuming the presidency after the death of Franklin D. Roosevelt, he had a lot of pressure, mainly because of the handling that he should have given to the issues related to the postwar period. For this reason, it can be concluded that the main purpose of this fragment about the early years of his presidency is to expose the pressure that Harry Truman had on his shoulders despite having a group of advisers, he had to assume the responsibility of being president, and all the consequences that this would bring him including the decision to use the atomic bomb. So the correct answer is B. President Truman was under intense pressure from the very beginning of his term of office.