Keller achieves her purpose of convincing the audience by using a fact. quotation. rebuttal. statistic.

fact

Explanation:

Convincing an audience about a particular subject requires that the person present facts capable of adequately informing the public about the subject. The facts must be based on evidence, which acts as evidence and gives confidence to the conformation to the group's understanding. An example of evidence is statistical data, which is a reliable way to prove a fact.

the answer is a)   a sentence of death costs the state "almost three times as much as a sentence of life in prison" (delon 147)

the sentence that best describes the tone of the passage from the radio broadcast compared to the passage from the book is b. the radio broadcast has a more surprised tone.

consider the text evidence: in the passage from the book, the description is more matter-of-fact. it is simply describing the things resembling little grey snakes, but there is no urgency in the description. on the other hand, in the passage from the radio broadcast, there is definetely urgency (you can tell from the expression used, "good heavens", which clearly indicates surprise.)