Step 1: Understanding the sentence.
The sentence is “We must help _______ poor.” Here, “poor” refers to poor people in general.
Step 2: Rule of article usage.
When we refer to a whole class or group of people (like the poor, the rich, the blind), we use the definite article “the.”
Step 3: Analyze the options.
(A) a: Incorrect — “a poor” would mean one poor person, which is not the intent.
(B) the: Correct — “the poor” means poor people as a whole.
(C) an: Incorrect — “an poor” is grammatically wrong.
(D) None of the above: Incorrect, since (B) is correct.
Step 4: Conclusion.
The correct answer is (B) the.