B. they are all assembled from a nucleic acid code.
Step-by-step explanation:
All living organisms on Earth are similar in that they are assembled from a nucleic acid code, specifically from the genetic material called DNA. DNA carries the instructions for the synthesis of proteins, which are the building blocks of life. The genetic information in DNA is used to create the unique characteristics of each species, but the fundamental structure of DNA is the same across all living organisms. This shared nucleic acid code is a key aspect of the unity of life on Earth.