Answer:
Armstrong had a difficult childhood: His father was a factory worker and abandoned the family soon after Louis's birth. His mother, who often turned to prostitution, frequently left him with his maternal grandmother. ... A local Jewish family, the Karnofskys, gave young Armstrong a job collecting junk and delivering coal.
Explanation:
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.