We can actually deduce here that the sentence from the passage that indicates that the source is not entirely credible is: "The age requirement for voting was enacted after the Civil War by the Fourteenth Amendment, setting the voting age at 21."
<h3>What is a credible source?</h3>
A credible sourceactually refers to the source that is reliable, trustworthy and true. It actually means a source which has firsthand information.
We see that the selected option is the sentence that that indicates that the source is not entirely credible because it's not clear what year the setting of voting age at 21 was ratified.
