The correct answer is: A. market efficiency
Market efficiency is the hypothesis that asset prices reflect all available information. In other words, it is impossible to consistently outperform the market by using publicly available information.
There are three levels of market efficiency: weak, semi-strong, and strong.
- Weak form efficiency states that current market prices reflect all past market prices. This means that it is not possible to use historical data to predict future prices.
- Semi-strong form efficiency states that current market prices reflect all publicly available information. This means that it is not possible to use news or other publicly available information to predict future prices.
- Strong form efficiency states that current market prices reflect all information, both public and private. This means that it is not possible to use any information, including insider information, to predict future prices.
In practice, it is generally accepted that markets are weakly efficient, but there is some debate about whether markets are semi-strong or strong efficient.