The Answer is C. Constructing
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.
Answer:
watch out for poison ivy oak, and sumac Kayla.
Explanation:
The comma goes right in between oak & and.
Can we please see the text?