As a signal travels though a medium, it attenuates (loses strength) and at some point will become indistinguishable from noise. To assure trouble-free communication, maximum cable lengths are set between nodes to assure that attenuation will not cause a problem. The maximum CAT-5 UTP cable length between two nodes for 10BASE-T is 100M.
The following answers are incorrect:
80 meters. It is only a distracter. 185 meters. Is incorrect because it is the maximum length for 10Base-2 500 meters. Is incorrect because it is the maximum length for 10Base-5