Since diffusion is the primary method one celled organisms use for material transport, the ratio of is an important factor for them

Ibelieve the answer is c. 

The rate that would change would be the  searching efficiency/attack rate. there are only two other rates in this model: the  growth rate of prey, and the  predator or consumer mortality rate.the  searching efficiency/attack rate is what indicates how effectively can a predator capture its prey whether in the searching process or actual capturing/attacking process.