Answer:
The correct answer is letter "C": strong-form efficient.
Step-by-step explanation:
The Efficient Market Hypothesis or EMH is the theory that beating the market is impossible because stocks are already accurately priced and reflect all available information so it is theoretically impossible to make a profit from any trading strategy. The EMH can be weak, semi-strong or strong.
The strong-from of the EMH states that all the private and public information is already reflected in the stock price, thus, investors cannot take advantage of the market.