The purpose of alliances such as the Triple Alliance and the Triple Entente was to

ACreate a mutually advantageous free trade association
BProvide mutual defense and support in case of attack
CCooperatively share resources in African colonies
DAvoid war

Verified Answer :

The purpose of alliances such as the Triple Alliance and the Triple Entente was to "b. Provide mutual defense and support in case of attack," since these were "block alliances".