D. suspenseful
Hope this helps
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:
A. Knowing that the attack might reach us in all too short a time, we
immediately began greatly to increase our industrial strength and
our capacity to meet the demands of modern warfare.
Explanation:
The attack is coming quickly so the logical thing to do is to prepare. The other examples are motivational or pathological statements while the first one (A) uses a clear and methodical string of thought to find a solution for the coming attack.
(If a picture type thing helps you: attack coming soon---what do we do?---begin to prepare for the attack immediately.)
