Which of these is least likely to be an adaptation?

D. A dalmatian learns to bark on command.  

An adaptation can be defined as single natural change or group of changes that occurs in an organism which supports it's survival in changing environment in which an organism is living with respect to time. Ants leave the anthill to search for food is an example of adaptation this may be due to scarcity of food in the anthill ants adapt to leave it to fetch food from other location. A cactus have a thick stem that allows it to store large amount of water. As, cactus is a plant which grows on dry desert regions where rainfall does not occur frequently. Therefore, cactus have thick stem to prevent water loss through transpiration. A spider spins web to capture prey is an adaptation, as it is a mode of deriving it's food by spreading a web on the surface and prey gets stick to the web and hence, get captured in the web. Spiders are evolved to get food in this way. A dalmatian learns to bark on command is human induced phenomena and not a natural process. Therefore, it is not a natural change in a dog but it is a human induced change. Hence, least likely to be an adaptation.  

answer: "circumcision is a common procedure in which the skin covering the tip of the penis is surgically removed."