To produce a fruit that has some characteristics of an orange and some of a grapefruit you would use the selective breeding technique of what

The answer is hybridization.

Hybridization represents crossbreeding of two different breeds, species or genera. It results in hybrids with some characteristics from one breed/species/genera and some from the other one. It could also have some new characteristics. For, example, a crossbreed of an orange and a grapefruit will have some characteristics of the orange and some of the grapefruit. This is an example of crossbreeding between two species of the same genera (Citrus) - orange is Citrus sinensis and grapefruit is Citrus paradisi.