To answer this question we first have to address the differences between exponential and logistic growth. We then have that the first one is related to those populations that grow until they reach a point known as load capacity when the individuals of that particular population, stop reproducing themselves. On the other hand, logistic growth refers to the increase in the number of individuals progressively, until they reach a point in which they are more abundant, but continues reproducing with each other.
These particular kinds of population growth depend on the scale of time used. For example, along a year, this group of organisms can increase their density exponentially, but at the end of this period, they can have logistical growth.
Having seen this, we could say then, that the graph with the Paremecium has a logistic growth, the graph of the sheep, none of them (or both if looked at lower time scales), and the graph of the elephant would have exponential growth.