The correct answer is'C' because it just gives us additional information,If you remove it from the sentence,it will make perfect sense.
Answer:
sarcastic
Explanation:
just read it its not sad,happy,cheerful
its straight up sarcastic
An appropriate summary for the article "A Most Troublesome Element" is the last option - C. Arsenic is a naturally occurring, poisonous element that has threatened the health of humans since the Middle Ages.
It clearly states what the whole article is about.
B Clear. They need to be clear in order to be a strong statement