When analyzing the credibility of a speaker, which of the following may be reasons not to trust what the speaker is saying? limited amount of evidence use of words like "always" and "never" emotional speech all of the above

All of the above contribute to the decrease in the speaker's credibility when delivering a speech.

A speaker must  provide the audience with evidence or reasoning.
A speaker must not exaggerate; that leans towards desperation to be believed, which can be taken as loss of credibility.
A speaker must not be emotional during a speech if the speech is meant to be formal/informative/persuasive (anything other than personal).

I hope I was able to be of help.