Memorability of speech is the quality of being easy to remember a speech. There are various techniques used in memorizing a speech like stressing the main points, sensibly connecting the concepts, using repetition of important ideas, using a strong ending to drive home key ideas and many more but "Using a loud voice, shouting key words" does not add to memorability of speech.
A is wrong because it’s a statement. B is the answer because it asks “why haven’t you” & that’s the example. C is another statement D is a demand, not a bandwagon fallacy