Final answer:
Donald Trump was a 'birther' who questioned President Barack Obama's status as a natural-born U.S. citizen, though Obama met the constitutional requirement through his American mother. The correct option is 4.
Step-by-step explanation:
Among the choices provided, Donald Trump was one of the conspiracy theorists known as 'birthers' who claimed that President Barack Obama was not a natural-born U.S. citizen. The birther controversy was centered around the eligibility requirements established in the United States Constitution for election to the office of president, specifically the natural-born citizen clause.
Though President Obama was indeed born to an American mother, thus conferring him natural-born citizenship status regardless of his birthplace, this did not stop Trump and others from fueling the debate. Trump's prominent role in the birther movement attracted considerable media attention and was a key feature of his political identity before he ran for president himself.