Final answer:
Option b. Bulbous corpuscles (Ruffini corpuscles) are considered tonic receptors because they respond to stimuli over a prolonged period and continually provide information on skin stretching and joint position changes.
Step-by-step explanation:
Tonic receptors are a type of sensory receptor that continue to respond to a stimulus over a prolonged period and provide a constant rate of firing as long as the stimulus is maintained. Among the options provided, the Bulbous corpuscle (Ruffini corpuscle) is considered a tonic receptor. These corpuscles primarily detect skin stretching and changes in joint position, continually providing the brain with information about these states. In contrast, receptors such as Lamellar (Pacinian) corpuscles are classified as phasic receptors because they respond with a burst of activity initially but quickly adapt to a constant stimulus and subsequently decrease firing.