Final answer:
The linear form of DNA is represented by chromosomes, which are linear structures composed of DNA and proteins and visible during cell division.
Step-by-step explanation:
The linear form of DNA is represented by chromosomes. In eukaryotic organisms, chromosomes are distinct linear structures made up of DNA and associated proteins; they contain the genetic instructions necessary for the life processes of an organism. DNA takes on this linear form when structured into chromosomes during the cell cycle, particularly when the cell prepares to divide. Chromatin, by comparison, is the less condensed form of chromosomes and is present when the cell is in phases of growth and maintenance.
In a resting state, DNA is wrapped around histone proteins to form nucleosomes, appearing like 'beads on a string' in the chromatin thread. Upon cell division, this chromatin compacts to form the distinct linear structures known as chromosomes. Thus, when considering the linear form that DNA takes during cell division, the correct answer is A: Chromosomes.