Which type of advertisement can contain explicit references to preferred gender?

The correct choice is shared living spaces because advertisements for this type of housing can contain explicit references to preferred gender, particularly due to the nature of communal living arrangements. In shared living situations, such as roommates in a house or shared apartments, it is often common for residents to seek individuals of a specific gender for reasons related to privacy, comfort, or lifestyle preferences.

This practice is generally permissible because it can be tied to the dynamics and agreements that often govern shared living situations, which may include the necessity for cohabitation policies to ensure compatibility among residents. In contrast, advertisements for other housing types, such as townhomes, single-family homes, or condominiums, typically do not allow for gender specifications as they are meant to appeal to a broader audience and are subject to stricter fair housing laws that prevent discrimination based on gender.