Which of the following can improve the tone of a presentation by making it sound more professional?

I found this from https://www.market-inspector.co.uk/blog/2017/02/speaking-habits-to-help-you-sound-professional I  ( I need to cite my sources )

Always remember to stand or sit with your back straight! Your posture is the first thing the audience will notice. First impression always matter!

Maintain visual contact with the audience! This shows that you are connected with your audience.

Remember that your listeners deserve your full attention. No one likes to listen to an emotionless presentation where the person speaking doesn’t seem mentally present.

Not everyone has front seats! Remember to speak loudly and make sure everybody is able to hear you. However, do not start yelling.

Body language and gestures make every presentation more engaging and vivid! Therefore, use these to emphasize important points. If you don not feel like it comes natural to use body language, it is better not to use it too much.  

Make yourself understood! Use words that your audience will understand and make clear the points that you are presenting. Fancy words or expression may only create confusion. Avoid emphasizing yourself and instead make it about the cause you are there for.

Use pauses! They can help you emphasize key points and create suspense. Your listeners will stay engaged and will be able to remember more of your presentation as they will connect it with a certain move or a certain moment of silence.

You need to interact and respond to questions! There will always be questions. Therefore, you need to make it feel more like a conversation. The more questions you ask and explain, the more involved and professional you will look.

the positive connotations of the words "pretty," "quiet," and "silence" give the excerpt a tone of nervousness. i think its this