Final answer:
The example of the plumber working for the hairdresser illustrates the convenience and flexibility of time banks, showing how individuals can trade services effectively without immediate reciprocity. The correct answer is option A).
Step-by-step explanation:
The detail "The plumber might not want a haircut, but he can work for the hairdresser and earn credit to use with someone else" best supports the central idea that time banks are a convenient way to get things done by providing a clear illustration of how this system facilitates the exchange of services without requiring a direct barter between two parties. It exemplifies the convenience and flexibility of time banking, where individuals can earn and spend credits for services according to their own needs, without the challenges presented by the direct barter system of a double coincidence of wants. By earning credits through services performed, which can then be used to receive different services in return, time banks simplify transactions in a modern, complex economy.