Which of the following conditions are necessary for a series to be classifiable as a weakly stationary process?

(i) It must have a constant mean

(ii) It must have a constant variance

(iii) It must have constant autocovariances for given lags

(iv) It must have a constant probability distribution
(A)(ii) and (iv) only (B)(i) and (iii) only (C)(i), (ii), and (iii) only (D)(i), (ii), (iii), and (iv)
C