unused options may have unexpected behavior

unused options sometimes are either ignored as options or put as leftover args. Example: `./program -X` would treat `-X` as a leftover arg if the `X` option has not been added, similarly, `./program -X -v` would ignore `-X` if `v` was added but `X` was not. Users should be notified about invalid options, ideally by failing the program and printing the help message. 