Which can eliminate the possibility of sexual partners getting hiv through body fluids, providing that both partners began the relationship free from infection?

If both of those sexual partners are faithful to each other, and only have sexual relations with one another, then there isn't a high probability that either of them is going to get HIV. If they want to be sure, they should use protection, such as condoms, to prevent getting HIV through body fluids. And they should always be honest with each other in case one of them has that disease.