Which of these allow nutrients to diffuse from the central canal to all the osteocytes within an osteon?

The correct answer is canaliculus.

An osteon is the functional unit of the compact bone and it is mainly comprised of bone cells, called osteocytes. Each osteocyte can connect with its counterparts through a network of canals which are called canaliculi. These microscopic canals participate in the transport of nutrients and metabolic byproducts.