The correct answer is A. Single-use plastic bags should be banned nationwide because they are harmful to wildlife and pollute waterways.
Step-by-step explanation:
In the introduction of an argumentative, the argument or claim of the author refers to a concise statement that expresses the author's position or perspective towards a topic and if possible mentions briefly the reasons that support this position.
This implies the sentence Damian needs to includes in the introduction to clearly present his argument and claims is "single-use plastic bags should be banned nationwide because they are harmful to wildlife and pollute waterways" because this statement shows the position of Damian in reference to using plastic bags once as his position is that this should be banned. Additionally, this statement briefly points out the reasons for this "they are harmful to wildlife and pollute waterways" that would be explained and supported with evidence in the body paragraphs.