"According to national standards for measuring square footage of a dwelling, which space should be included?"

attached accessory apartment

Explanation:

According to national standards for measuring the square footage of a dwelling, specifically on Attached Single Family Square Footage, the space that must be included in measurement is Attached Accessory Apartment or Accessory Dwelling Unit which is described generally as a form of a second, but smaller living unit on the same plot of land or grounds or attached to a single-family home.

Hence, the right answer is Attached Accessory Apartment

you should try adrenaline. it kicks in in situations like this.