In the oneida community that existed in new york state from 1840 to 1880, the community members were all married to one another—that is, all the men in the community were married to all the women, and all the women were married to all the men. this is an example of:

Complex Marriage is the correct answer.

Explanation:

The marriages in which all the men of community are married to all the women of the community it is known as Complex marriages. The sexual relations are also permissible as long as  there was mutual agreement.  

The Oneida community was founded by John Humphrey Noyes, it was one of the most successful Utopian socialist communities in US. Noyes was the son of wealthy New England businessmen and was influenced by evangelist Charles Finney. In 1836 he wrote “Battleaxe letter” and argued for free love.

answer; (religion)