The correct answer is: A. coefficient risk volatility
Beta coefficient is a measure of the volatility of a stock relative to the market. It is calculated by regressing the stock’s returns against the market’s returns. A beta of 1 means that the stock moves in perfect correlation with the market, while a beta of 0 means that the stock is not correlated with the market at all. A beta of greater than 1 means that the stock is more volatile than the market, while a beta of less than 1 means that the stock is less volatile than the market.
Option B is incorrect because it refers to market risk volatility, which is a measure of the overall volatility of the market. Option C is incorrect because it refers to stock market volatility, which is a measure of the volatility of the stock market as a whole. Option D is incorrect because it refers to portfolio market portfolio, which is a measure of the risk of a portfolio of stocks.