Both are right... the junctional epithelium is entirely on enamel and apically extends upto CEJ. (/Healthy periodontium)
Embryologically, the Junctional epithelium/epithelial attachment originates from REDUCED ENAMEL EPITHELIUM (REE;later replaced by oral gingival epithelium);
REE covers the coronal portion only... so JE is ENTIRELY ON ENAMEL.
BUT epidemiologically, the MC anatomy of CEJ is cementum overlapping enamel... so JE in such cases is not entirely on enamel but partly on cementum (a little!). But in the questions you should ASSUME that the CEJ is a butt joint (enamel and cementum meet at knife edge)... So if the question asks you where is CEJ located, the answer is ENTIRELY on ENAMEL (embryologically)Mayank. 😀
