How is the strength of a stimulus at a receptor transmitted to the sensory nerve?

How is the strength of a stimulus at a receptor transmitted to the sensory nerve?

frequency of action potentials from the receptor are proportional to the stimulus strength

size of action potentials from the receptor are proportional to the stimulus strength

by integrating the various receptors for the stimulus

the size of the receptor generator potential is proportional to the stimulus strength

The frequency of action potentials from the receptor are proportional to the stimulus strength.