Explain how to construct a positive$-$alpha trading strategy if stocks that have had relatively high returns in the past tend to have positive alphas and stocks that have had relatively low returns in the past tend to have negative alphas.

$($Select the best choice below.$)$

A$.$ You buy stocks that have done poorly in the past and sell stocks that have done well.

B$.$ You buy stocks that have done well in the past and sell stocks that have done poorly.

C$.$ You cannot construct a positive$-$alpha trading strategy$$risk$-$adjusted returns can never be predicted.

D$.$ You cannot construct a positive$-$alpha trading strategy$-$a positive$-$alpha trading strategy is an arbitrage opportunity.