Incipient caries is seen radiographically as a radiolucency that has:

a. penetrated less than halfway through the enamel.
b. penetrated over halfway through the enamel but did not reach the DEJ.
c. penetrated at or through the DEJ but less than halfway through the dentin toward the pulp.
d. penetrated over halfway through the dentin toward the pulp.

a. Incipient caries appear as a radiolucent notch in the enamel only. The radiolucency is less than halfway through the enamel.