Answer: I would contend that the right answer is prostitution.
Explanation: Just to elaborate a little bit on the answer, it can be added that those three artists—all French, since prostitution became a subject of great interest in France and other parts of Europe in the nineteenth-century—explored the traditional theme of prostitution, although with a different approach: a very contemporary one, which showed the crude reality of it openly and without reservations. Manet's <em>Olympia </em>(1865) caused a great scandal when he exhibited it at the Paris Salon, in spite of its references to classical models, such as Titian's <em>Venus of Urbino</em>. He portrayed a prostitute that looked at the viewer without any shyness. In addition, both Degas and Toulouse-Lautrec painted brothels. Examples of this are <em>The Madam's Name Day</em> (1876), by Degas, and <em>Salon de la Rue des Moulins</em> (1894), by Toulouse-Lautrec.