Which of the following pairs are the best examples of homologous structures? (a) bat wing and human hand(b) owl wing and hornet wing(c) porcupine quill and cactus spine(d) bat forelimb and bird wing(e) australian mole and north american mole

(a) bat wing and human hand

Explanation:

The homologous structures are structures at living organisms that are the same, very similar, or have the same function, despite the organisms having different appearance. This can mostly be seen in the bones of the animals, and this type of structures more often then not suggest a distant common ancestor between the species. Usually the homologous structures appear among animals from the same class, so it can be expected that animals from the mammalia class can have these structures, or animals from the reptilia etc. In this case we have the bat wing and the human hand. Both have similar bone structure, and the function of the bones in the bat wing and the human hand is also similar. Both of them are in the class of mammalia, and they do share a very distant common ancestor in the small shrew-like mammals during the reign of the dinosaurs.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.

the law of original horizontality explains:   why rocks appear in layers. correct answer: b the law suggests that all rock layers are originally laid down (deposited) horizontally and can later be deformed.   the principle is used by geologists to make assumptions about the relative ages of sedimentary rocks.