If two variables, $x_t$ and $y_t$ are said to be cointegrated, which of the following statements are true?

i) $x_t$ and $y_t$ must both be stationary


ii) Only one linear combination of $x_t$ and $y_t$ will be stationary


iii) The cointegrating equation for $x_t$ and $y_t$ describes the short-run relationship

between the two series


iv) The residuals of a regression of $y_t$ on $x_t$ must be stationary
(A)(ii) and (iv) only (B)(i) and (iii) only (C)(i), (ii), and (iii) only (D)(i), (ii), (iii), and (iv)
A