You are analyzing a time series and want to determine its stationarity. You also want to determine theorder of
autoregressive models.
How are the autocorrelation functions used?

A.
ACF as an indication of stationarity,and PACF forthe correlation between Xt and Xt-k not explained by their
mutual correlation with X1 through Xk-1.

B.
PACF as an indication of stationarity,and ACF forthe correlation between Xt and Xt-k not explained by their
mutual correlation with X1 through Xk-1.

C.
ACF as an indication of stationarity,and PACF to determine the correlation of X1 through Xk-1.

D.
PACF as an indication of stationarity,and ACF to determine the correlation of X1 through Xk-1.