The correct answer is A. inefficient market hypothesis.
The efficient-market hypothesis (EMH) is a theory that states that asset prices reflect all available information. In other words, it is impossible to beat the market by using any information that is already available to other investors.
The EMH is based on the assumption that markets are efficient, which means that prices reflect all available information. This means that if there is any information that could be used to predict future prices, it is already reflected in the current price.
There are three forms of the EMH: weak, semi-strong, and strong. The weak form of the EMH states that past prices cannot be used to predict future prices. The semi-strong form of the EMH states that all publicly available information is already reflected in prices. The strong form of the EMH states that all information, both public and private, is already reflected in prices.
The EMH is a controversial theory, and there is no consensus among economists about whether it is true or not. However, it is an important theory in finance, and it has been used to develop many investment strategies.
The other options are incorrect because they do not accurately describe the efficient-market hypothesis. Option B, efficient stock hypothesis, is not a commonly used term. Option C, inefficient stock hypothesis, is the opposite of the efficient-market hypothesis. Option D, inefficient market hypothesis, is the correct term for the theory that states that stocks are in equilibrium and impossible for investors to beat market.