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A
Pay taxes
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B
Obey the law
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C
Serve on a jury
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D
Drive safely
Why this is the answer
JURY DUTY is a responsibility for US citizens specifically — non-citizens cannot serve on federal or state juries. Serving on a jury is how citizens participate in the justice system. USCIS Question 50: 'What is one right or freedom from the First Amendment?' is different from Question 49: 'What is one responsibility that is only for United States citizens?' Key answer: SERVE ON A JURY. Other citizen-specific responsibilities: VOTE in federal elections (non-citizens cannot legally vote in federal elections). Compare: responsibilities of ALL people in the US include obeying laws and paying taxes — these apply to non-citizens too.
Source: USCIS Civics Question 49 — Citizen Responsibilities