There are many techniques that can contribute to the memorability of a speech, for example stressing the main points and explaining them well, linking the ideas in a logical way and providing a strong conclusion.
One technique that does not support memorability is shouting loudly key words: they might remember you but not the content of the speech.
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I would say the 1st one is the only one correct. The 2nd one should be who, the 3rd one should more and likely be whom, and the last one should probably be who. I don't know if I'm 100% though. I hope I helped.
