Both the groups of fruit flies were kept in the containers of different volumes (space). These groups were observed for period of 40 days. The graph shows that the population of both the flies has reached stagnation point, above which they can not grow. This is because the amount of space available to them is limited.
Since the fruit flies in container B had more space, they increased more as compared to flies in container A.
Hence, the correct answer is (b) a fly population with more available space will grow larger than a population with less space.