Final answer:
Elk Cloner caused limited damage due to its reliance on the physical sharing of floppy disks for propagation, which constrained its spread and impact.
Step-by-step explanation:
The Elk Cloner virus caused so little damage because d. it required the sharing of floppy disks to spread. In the era when Elk Cloner was created, the exchange of floppy disks was the primary method for the virus to move between computers.
Unlike modern viruses that can spread quickly through networks and email, Elk Cloner's propagation was limited to physical interactions. This inherently slowed the rate of transmission and contained the virus to a smaller number of systems, thereby limiting the extent of the damage it could inflict.
The elk cloner virus caused relatively little damage because it required the sharing of floppy disks. This limited its ability to spread quickly and widely compared to viruses that can propagate through the internet or other means. While its signature was quickly distributed, meaning that antivirus software could detect it, the fact that it wasn't an armored virus and that it was caught by most default firewalls also contributed to its limited impact.
Therefore the answer is d. it required the sharing of floppy disks.