"The white toga is under the dress."
Translation:Toga candida sub stola est.
As a rule, only male citizens wore togas. The Romans sometimes are referred to as gens togata, "the toga-wearing people" (Aen. 1.282), but gens togata for Virgil only refers to male citizens, not women, not slaves, not freedmen. This DL sentence is probably an oblique reference to the infamous incident in which Claudius Pulcher violated the ceremony of Bona Dea dressed as a woman. The interesting exception to the rule concerns prostitutes and adulteresses wearing a type of toga, but the evidence for this custom is limited (esp. the Lex Iulia) and a prostitute was identifiable in a variety of ways. The secondary literature on Roman prostitution covers the matter. Thomas McGinn has two books on the subject, one of which is Prostitution, Sexuality, and the Law in Ancient Rome (2nd edition; Oxford, 2003) esp. pp. 156-171. Here's a solid online overview + secondary literature: https://www.theposthole.org/read/article/349
Because it's in the ablative case and not the accusative case. The way I understand it, "sub" uses the ablative case to indicate a location and the accusative case to indicate a destination. (i.e., "sub stolam" = "[located] under the dress", while "sub stola" = "[headed] under the dress")
I'm no expert, but I think that the word order in "stola sub est" is very unlikely, and should certainly not be among the accepted answers. I've not seen any examples in this course of prepositions following the noun they govern. sub is a preposition, and the name for that type of word, with its pre prefix, itself suggests that a preposition should come before the noun it governs.