Carson Used to Really Enjoy Lime Sherbet,and When He Was

Carson used to really enjoy lime sherbet,and when he was in Mexico,he tried frozen lime margaritas.After his fourth margarita,Carson became extremely ill.Now he finds that even the sight of lime sherbet in a bowl can make him feel queasy.What is the unconditioned stimulus in this example

A)  the queasiness that Carson feels when he sees lime sherbet 
B)  the sight of lime sherbet 
C)  the lime margaritas that Carson consumed 
D)  the illness that followed the fourth margarita