$($d$)$ Explain how cross$-$validation for classification problems can be adapted to be applicable to time series prediction. $(5)$

$($e$)$ Describe how cross$-$validation should be applied to evaluate the performance of time series predictive models. In your discussion, first discuss the limitations of the standard cross$-$validation approach above for non$-$temporal data. Then explain the approach to cross$-$validation for time series, and the justify this approach. $(8)$