Final answer:
Italy joined the Allies in World War I through a secret treaty to gain Austrian lands, leading to its surprise attack on Austria.
Step-by-step explanation:
The reason why Italy surprised everyone by punching Austria in World War I is a. Italy joins the Allies in a secret treaty to gain Austrian lands. Initially, Italy had declared neutrality when the war erupted, but underlying tensions and desires for territorial expansion drove Italy to reconsider its position. In May 1915, after securing the promise of Austrian territories through a secret agreement with the Allies in April, Italy entered the conflict on the side of the Allied Powers, turning against its former allies of the Central Powers.