What does the error message "The underlying connection was closed: An unexpected error occurred on a send" typically indicate in a network or web application context?
a. The client-side application has lost its network connection or experienced a timeout during data transmission.
b. The server-side application has encountered an issue with its database connection.
c. There is a mismatch between the server's and client's encryption protocols.
d. The web server's certificate has expired or is invalid.