According to the efficient market hypothesis, in order to earn abnormally high returns, an investor would need to have exclusive information

Unexploited profit opportunities

A$.$ help investors generate abnormally high returns in the long run.

B$.$ are quickly eliminated by arbitrage.

C$.$ are quick to disappear.

D$.$ are split equally among all investors.

Announcements of already$-$known information

A$.$ fail to affect stock prices.

B$.$ generate unexploited profit opportunities.

C$.$ reduce stock returns.

D$.$ improve forecasts of stock prices.