Question

what are the main growth factors that regulate the check points of the cell cycle? neurological signals pheromones structural proteins hormones

Explanation:

Hormones are chemical messengers that can regulate various physiological processes, including the cell cycle. Neurological signals are related to the nervous system and not directly the main growth factors for cell - cycle checkpoints. Pheromones are used for communication between organisms (especially in terms of mating in some species) and not for cell - cycle regulation. Structural proteins provide support and shape to cells but are not the main growth factors regulating cell - cycle checkpoints.

Answer:

hormones