The best option is A) by providing a common calendar. A common calendar can be used to check availability and schedule appointments, making the process of setting appointments easier.
However...
All of the options (A, C, D, and E) could potentially make setting appointments easier on a computer network.
A) A common calendar can be used to check availability and schedule appointments.
B) Workloads could be reassigned to enable attendance at appointments, but this is not directly related to the use of a computer network.
C) Invitations to appointments can be sent electronically through the network.
D) Telephone calls can be made through the network.
E) Electronic reminders can be sent through the network to help ensure that appointments are not forgotten.