SAT Question 90eed2e5: Inference From Sample Statistics And Margin Of Error answer and explanation with Desmos solution

Choice C is correct. Because a random sample of the city council was polled, the proportion of the sample who supported the bill is expected to be approximately equal to the proportion of the total city council who supports the bill. Since $6$ of the $20$ polled, or $30\%$, supported the bill, it can be estimated that $50\times 0.3$, or $15$, city council members support the bill.