Final answer:
The erroneous statement in the question is that D. the root canal is where blood vessels and nerves pass into the pulp cavity, which is incorrect. Rather, the root canal is part of the pulp cavity within the tooth's root that contains these structures.
Step-by-step explanation:
If you were showing a friend a cross-section of a tooth, you could not use the statement that 'The root canal is where blood vessels and nerves that supply and innervate the tooth pass into the pulp cavity' to explain it. Instead, you would point out that enamel is the hardest tissue in the body and covers the crown of the tooth. You could also mention that the crown lies above the gingiva, or gums, and that the neck of the tooth sits in the alveolar process of the jawbone. The root canal, contrary to the initial misconception, is actually the area within the root of the tooth where the pulp cavity houses blood vessels and nerves, not where they pass into it.
A. Enamel is the hardest tissue in the body: Enamel covers the crown of the tooth and is the hardest material in the human body, providing protection to the underlying structures.
B. The neck of the tooth sits in the alveolar process of the jaw bone: The neck of the tooth is located at the gum line, and it is held in place by the alveolar process, which is part of the jaw bone.
C. The crown of the tooth lies above the gingiva: The crown is the visible part of the tooth that extends above the gum line, also known as the gingiva.