Answer:
b. Eukaryotic cell structure
Step-by-step explanation:
LUCA - the last universal common ancestor with its structure looked more like bacteria: small, single-celled organism with a ring-shaped coil of DNA which floated freely within the cell (no nucleus like eukaryotic cell). It is estimated LUCA lived 3.5 to 3.8 billion years ago. The genetic code of LUCA was based on DNA and it did the functions such as transcription and translation.