Which of the following observations does not necessarily contradict semi-strong form efficiency of the stock market? Choose all answers that apply.

A. Insiders can earn abnormal return by trading on their private information

B. A trading strategy based on book to market ratio outperforms the market index. However, up to 95% of the outperformance can be explained by risk.

C. A momentum strategy that buys past 12-month winners outperforms the market every month after controlling for the level of risk

D. Average stock market raw return is higher than average bond market return

A brief explanation would be very welcomed, along with any tips and tricks to distinguish the different forms of EMH-- I am really struggling to understand the topic. Thank you in advance.