Answer:
Third sentence
Explanation:
In the first sentence, therefore is used for reasoning
ex: Therefore, dirty water is bad for the environment because it can make people sick
The second sentence is a run on sentence so it would not be correct.
The effect that the framing of Frankenstein had was that it suggeted the threat of the narrator and was vital in illustrating the theme.
<h3>What was the effect of the framing?</h3>
The effect of the framing was vital in Frankenstein ad it allows for deep exploration of the theme.
It should be noted that frame stories are used in establishing emotions and interest in the minds of the readers before the story begins.
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The correct sentence is B.