Final answer:
Life's organic building blocks were formed when simple organic molecules combined. These molecules eventually formed more complex structures such as RNA, which could encode genetic instructions and catalyze reactions, suggesting an early "RNA world" before the advent of DNA and proteins. The correct option is B.
Step-by-step explanation:
The question about life's organic building blocks relates to how these basic components of life were initially formed on Earth. The answer to the question is that life's organic building blocks were formed when simple organic molecules combined. Initially, the Earth's environment facilitated the formation of simple organic compounds such as amino acids and nucleotides.
These compounds are the building blocks of proteins and nucleic acids, respectively. Over time, a multitude of chemical reactions led to the creation of more complex and stable organic molecules, paving the way for the emergence of basic cells.
An important concept related to this topic is the RNA World Hypothesis, which proposes that RNA may have been the first organic molecule to evolve. Unlike DNA and proteins, RNA can both encode genetic instructions and catalyze chemical reactions, providing a potential solution to the "chicken-and-egg" problem of which macromolecule came first in the early development of life.