What are three ways someone can be considered jewish

There are three criteria according to which people define themselves as Jewish: by religion, by culture and by ancestry. Believers in Judaism are considered Jewish; attachment, observance of traditions, norms, cultural values, knowledge of history make it for the second criterium; and if somebody´s genealogy includes Jewish ancestors, so that person is seen as a Jew, too.

Explanation:

the triple alliance. germany and austria-hungary were already allies by 1879 when, worried about a threat from russia, they formed the dual alliance. italy joined the group in 1882. there was a concern about a possible attack from france and the alliance needed powerful friends to defend it.