Which group in this food web would most likely have the greatest biomass? . . . a) owls
b) oats
c) rats
d) snakes

There exist a food web where oats are consumed by rats and crickets. Thus, the answer to the question above is letter "B. Oats". Aside from that, we know for a fact that oat is one of the primary source of food of many consumers. As basic food source, its supply should be abundant.