Which of the following is an example of a sexual orientation?

The example of a sexual orientation among the choices provided is "Lesbian." Sexual orientation refers to the pattern of emotional, romantic, or sexual attraction one feels toward others, typically categorized by the gender of the individuals that someone is attracted to. In this case, "Lesbian" specifically denotes women who are attracted to other women, thereby fitting the definition of a sexual orientation.

On the other hand, "Transgender" refers to a person's gender identity rather than their sexual orientation, as it relates to how individuals perceive themselves in terms of gender and not necessarily whom they are attracted to. "Cross-dresser" describes a practice where individuals wear clothing typically associated with a gender different from their own, which does not inherently define their sexual orientation. "Celibate" refers to a lifestyle choice to abstain from sexual activity, which also does not pertain to one's attraction to others or sexual orientation. Therefore, "Lesbian" stands out as the term that specifically encapsulates a type of sexual orientation.