Question

the earth consists of a variety of different organisms. despite their diversity, however, some similarities on the structural and metabolic levels may be seen. these similarities can be attributed to
a. similarities in organisms habitats and niches.
b. similarities among organisms in their proteins and nucleic acids.
c. the ability of all organisms to interbreed and produce new species.
d. the ability of organisms to readily adapt to sudden environmental changes.
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Explanation:

地球上的生物具有多样性，但在结构和代谢水平上存在一些相似性。这些相似性可以归因于生物在蛋白质和核酸方面的相似性。生物的栖息地和生态位、适应环境变化的能力以及产生新物种的能力都不是生物在结构和代谢水平上相似性的主要原因。

Answer:

B. similarities among organisms in their proteins and nucleic acids.