What keyword covers unhandled possibilities?

The keyword that covers unhandled possibilities in the C programming language is "default".

In the context of a switch statement, the "default" keyword is used to specify the code block that should be executed if none of the cases match the value being tested. It acts as a catch-all for unhandled possibilities.

Here is an example to illustrate its usage:

switch (variable) {
  case value1:
    // code to be executed if variable matches value1
    break;
  case value2:
    // code to be executed if variable matches value2
    break;
  default:
    // code to be executed if variable does not match any of the cases
    break;
}

In the above example, if the value of the variable does not match any of the cases (value1 or value2), the code within the "default" block will be executed.

Please note that the "default" keyword is optional in a switch statement. If it is not included and none of the cases match, the program will simply continue execution after the switch statement.

I hope this explanation helps! Let me know if you have any further questions.