If the program does not handle an unchecked exception:
a.)
the program is halted and the default exception handler handles the exception
b.)
the program must handle the exception
c.)
the exception is ignored
d.)
this will cause a compilation error

a.) The program is halted and the default exception handler handles the exception

Explanation: If a exception is left out by the program handler then the processing is stopped and the control of exception handling is done to another handler. The unchecked exception is thus handled by the default exception handler.

Exception occur in the executing programs that try to stop the function by terminating it .The method used for the handling of the program is try catch and throw technique. Unchecked exception are found while the run-time and thus target the processing of the program.Thus,the correct option is option(a).

Other options are incorrect because the current program cannot handle the exception as it has left it unchecked, exception cannot be ignored because it stops the program and compilation error will not be caused.