Question

in which specimen were cells first identified?
microorganism
cork bark
dna
mitochondrion

Explanation:

In 1665, Robert Hooke used a primitive microscope to observe cork bark. He saw small, box - like structures which he called "cells". Microorganisms were observed later by Antonie van Leeuwenhoek. DNA was discovered much later through various scientific investigations. Mitochondria were also discovered after the initial discovery of cells.

Answer:

cork bark