If the sentence in question is a statement (ends with a period), I would probably "however" as your transition word.
Answer:
Stop Littering to Save Animals
Explanation:
Pathos is used when you are making an emotional argument
logos is used when you are making a Logical argument and
ethos is used when you are using some one else to support your argument
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“This could use more explanation/length.”
Supposed :)
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