Well without full context I would assume Trench Warfare because thats what 3 1/2 of the 4 year wars where full of.
"B. Decrease of
<span> investments in the same stock</span>" is the correct answer. When a stock's value decrease, many investors often withdraw their funds, thus leading to further decline.
The famous leader which helped kick start European nationalism is A) Napoleon. Napoleon is renown for being a "French military and political leader who rose to prominence during the French Revolution and led several successful campaigns during the Revolutionary War."