Answer:
The alliance system, which were the triple alliance formed by Germany,Italy and Austria-Hungary and the Triple Entente formed by UK,France and Russia.
The alliance system had caused great suspicion among the nations, as the alliance system was meant to be kept secret. The nations would be wary that they were to start war as they found backups for themselves.
It also support a nation's will to start a war as they would have back up, this urged WWI to happen.For example, with the support of Germany (blank cheque) Austria-Hungary sent an ultimatum to Serbia,which was impossible for Serbia to fulfill, finally lead to the outburst of WWI.
In addition, the system would enlarge the war scale to become a world war as one another would be drag into the war if one were involved.
Explanation:
B. both were total wars involved countries entire populations(apex)
