Final answer:
Carl Woese discovered the three-domain system of life, which categorizes organisms into Archaea, Bacteria, and Eukarya, based on differences in 16S rRNA gene sequences. Option c is correct.
Step-by-step explanation:
In the 1970s, American microbiologist Carl Woese and his colleague George Fox made a ground-breaking discovery using the gene sequences for small subunit ribosomal RNA (16S rRNA). They determined that a type of bacteria they called archaebacteria, now known as Archaea, were significantly different at the genetic level from other bacteria and eukaryotes.
This led them to propose a three-domain system of life, which included Archaea, Bacteria, and Eukarya, based on these genetic differences. As a result, Carl Woese is credited with the discovery of the three-domain system of life, which categorized organisms into distinct groups that share a common ancestral cell Type. Therefore, the correct answer to the student's question is c) The three-domain system of life.