Answer: A. The Fischer projection shows an aldehyde at C1 and the characteristic OH arrangement of D-glucose. As population density rises with a fixed supply of the only limiting resource, competition reduces the amount available per individual and slows population growth, tending to return the population towards carrying capacity.

B: reverses the effect of increasing density on the resource available per individual. C: misidentifies glucose as fructose; the displayed structure has a terminal aldehyde group. D: treats a fixed resource supply as density-independent, although its availability per individual changes with population density.

Remember: density-dependent factors tend to counter changes in population size relative to carrying capacity.