Suppose that your friend brags about his ability to make accurate predictions about financial market movements using only historical returns. He says $$it is totally pointless to keep track of company earnings. All you need to do is smart statistical analysis of prices and make buy$/$sell decisions based on that$.$ If it turns out that strategies such as your friend$$s really achieve superior abnormal returns over longer horizons, financial markets are $\_\_\_\_\_\_\_\_\_\_.$

A$.$

Semi$-$strong form efficient

B$.$

Strong form efficient

C$.$

Weak$-$form efficient

D$.$

Not even weak$-$form efficient