The correct answer is the option (D) Both are not a mammal, are multicellular, and are heterotrophic.
Keys in biology are used to identify the different species based on the easily identifiable features of the organism. A dichotomous key consists of a series of questions on features like habitat, mode of nutrition, class to which they belong and other features, with each question having two answers describing the characteristic features of an organism. The series of questions begin with a broader characteristic feature becoming narrow gradually and helping in the identification of the organism.
Both the house sparrow and a cobra cannot synthesize their own food and depend on other organisms for food. Hence they are heterotrophic. They are multicellular in nature. A cobra belongs to the class Repltiles and a house sparrow belongs to the class Aves. Thus, a house sparrow and a cobra are similar to each other in being multicellular, heterotrophic and not belonging to the class mammals.