Which event sparked the onset of world war i?
a.
germany's invasion of belgium
b.
great britain's declaration of war on germany
c.
the mobilization of russia's armies
d.
the assassination of the heir to the austro-hungarian throne
e.
austria's seizure of bosnia and herzegovina

Germany's invasion of Belgium sparked the onset of World War I

Explanation:

The reason why world war 1 started was that Germany invaded and entered Belgium. Because it wanted to attack France from the northern side. Also it had to go through and cross the borders of Belgium but this was out rightly rejected by the officials of Belgium.

So as a result of this refusal, Germany decided to invade and enter Belgium by force also on 4th of August in the year 1914 and decided to attack France also there after.

to act quickly in times of danger to the united states

because you have to act quickly if you want to live/survive.

the  seven  days  battles  were  a series of seven battles over seven  days from june 25 to july 1, 1862, near richmond, virginia,  during  the american civil war. the  seven  days ended with mcclellan's army in relative safety next to the james river, having suffered almost 16,000 casualtiesduring  the retreat.