The Exposure Coefficient $b = \frac { \operatorname { Cov } ( P , S ) } { \operatorname { Var } ( S ) }$

The exposure coefficient $b = \frac { \operatorname { Cov } ( P , S ) } { \operatorname { Var } ( S ) }$ in the regression $P = a + b \times S + e$ informs

A) how much of a foreign currency to sell forward.
B) the part of the variability of the dollar value of the asset that is related to random changes in the exchange rate.
C) captures the residual part of the dollar value variability that is independent of exchange rate movements.
D) how many call options to write.