The correct answer is D. Competition.
Explanation
A limiting factor is a term that refers to the scarcity factor of a resource that limits the development and evolution of a specific species or process. According to what is described in the question, it can be inferred that the limiting factor of toucans is competition because the great hornbill lives in the same tropical forest as the toucan, it feeds on the same foods as the toucan: fruit, insects, and walnuts. So, competition for the same resources is a limiting factor for toucans since the absence of food can affect their development. So the correct respect is the D. Competition.
