Which of the followings is the MOST accurate?

The signaling effect of foreign exchange intervention...

a.works only in sterilized intervention.

b.can alter the market's view of exchange rates independent from the stance of monetary and fiscal policies.

c.cannot cause an immediate exchange rate change when bonds denominated in different currencies are perfect substitutes.

d.cannot cause an immediate exchange rate change when bonds denominated in different currencies are imperfect substitutes.

e.works both in sterilized and unsterilized interventions.