our broker suggests that you can make consistent excess profits by purchasing stocks on the

$20$th of the month and selling them on the last day of the month. If this is true, then:

A$)$ the market violates at least weak$-$form efficiency.

B$)$ prices follow a random walk.

C$)$ the market is only semi$-$strong$-$form efficient, but not weak$-$form efficient.

D$)$ insiders will be the only investors to profit