understand that they are models and they are completely used to that. they have to be. look at the fashion shows, their only outfits ARE their underwear. meaning they arent stipping to their underwear to change outfits in a big room full of people, their stripping nude to put on different underwear. so they cant refuse to be naked in front of people, its just not possible if your a model, and if your self consious or afraid to be naked infront of people then modeling is deffinately not for you. I'm sure they dont really think about it since they are all girls and they know the people around them are all professionals, including the photographers, makeup artist, ect...also they obviously do cover up themselves with their arms too. does that answer your question?
Did you notice in that picture that they all have their left leg bent apart from Karolina, who has her right leg bent? Also, Adriana's left hand is on her heel while the other girls' left hands are on their hips. I just think it's a bit strange that they didn't make them all pose exactly the same. I think it would have looked better.