At the end of your presentation the main points should be

The answer is: Summarized

Presentation could often take more than 45 minutes and it is very hard for most audiences to actually pay attention to the whole thing and remember every single points that you want to conveys.

Summarizing your points at the end of your presentation would help the audiences to remember the points that they might've missed during the presentation.

d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."

citizens were able to charge more for their goods and services