Final answer:
Gender identity is not specifically mentioned in Title VII of the Civil Rights Act of 1964, but courts, including the Supreme Court, have interpreted the Act to include protections against discrimination based on gender identity.
Step-by-step explanation:
The aspect that is not specifically mentioned in Title VII of the Civil Rights Act of 1964 but has been interpreted by courts to be inclusive of this protection is c) gender identity. Initially, Title VII explicitly prohibited discrimination in employment on the basis of race, sex, national origin, and religion. It was through legal interpretation and key Supreme Court rulings, like the landmark case of Bostock v. Clayton County, Georgia, that the Act's protections were extended to include discrimination based on sexual orientation and gender identity, understanding such discrimination as inherently related to discrimination on the basis of sex.