If the Central Banks of the World Chose to Diversify

If the central banks of the world chose to diversify their foreign-exchange reserves away from the dollar and into the euro,

A) this would have the result of a strengthening of the value of the dollar.
B) this would have the result of a weakening in the value of the dollar.
C) this would not have much impact, as the information would be lost in the day-to-day volatility of exchange rates.