Final answer:
The least volatile stock in a rising market is the one with a beta of 0.5, as it indicates lower volatility compared to the overall market.
Step-by-step explanation:
In a rising market, the stock that is least volatile is C) A stock with a beta of 0.5. Beta is a measure of a stock's volatility in relation to the overall market. A beta of 1 means the stock's price tends to move with the market. A beta greater than 1 indicates that the stock is more volatile than the market, while a beta less than 1 indicates that the stock is less volatile. Therefore, a stock with a beta of 2.0 (option A) is considered to be more volatile, as it would theoretically move twice as much as the market. An alpha of 2.0 (option B) or 0.5 (option D) is a measure of performance on a risk-adjusted basis and does not directly relate to volatility. Instead, alpha represents the excess return of a stock relative to the return of a benchmark index.