Final answer:
The likely cause of the connectivity issue is that the switches are not connected together using cross over cables. Considering as option number a, b, c and d, option number b is correct.
Step-by-step explanation:
Jessica is facing a connectivity issue where the computers connected to a switch are unable to communicate with the rest of the network. Considering the given options, the most likely cause of this issue is that the switches are not connected together using cross over cables.
Cross over cables are used to connect similar devices, like switches, directly to each other. If the switches are not connected using cross over cables, the data cannot be properly transmitted between the switches, resulting in the computers being unable to communicate with the rest of the network.
To resolve this issue, Jessica should ensure that the switches are connected together using cross over cables or use a switch with auto-MDI/MDIX feature to automatically adjust the connection.