You’ve done a large series of experiments, growing different combinations of crop plants together. Which of the following experimental plots would identify species that would be good candidates for companion planting (being planted together) in a commercial situation? The goal is to maximize the yield of each species planted, and increase overall yield compared with single-species plantings. 

Any combination of species that includes the “big producer” in the suite of crops you’re interested in.

Combinations where grams/individual is higher than it is in each monoculture.

The combination of species that gives the largest overall biomass per plot.

Combinations where grams/individual is particularly high in monocultures—meaning that intraspecific competition doesn’t affect the species very much.