How the fuck can an ANIMAL be willing to marry??????
If we first assume that marrying involves husband and wife, two samples of endless varieties of endless animal expressions, under a single circumstance (or constant to be), or even only one variety of those endless expressions represented at least twice to form the constant, the animal requires only to choose between three options: husband and wife, husband and husband, wife and wife.
Good question, simple answer.
There is more to the answer than the question requirements though. In the context of the question a fourth option is irrelevant and three options conclusive and direct. However, after the animal has already willed, a fourth option to be constant can also be included within the comprehension of marriage to proceed in its own unique conditions: wife and husband.
Applied mathematics.