Final answer:
The graph representing the lowest level of standard deviation for the highest level of return at each risk level in a portfolio is known as the efficient frontier.
Step-by-step explanation:
The graph you’re asking about, which shows all the possible combinations of the assets in one's portfolio that yield the lowest level of standard deviation for the highest level of return at a particular risk level, is known as the efficient frontier.
The efficient frontier is a concept from the field of portfolio theory in finance, which demonstrates how an investor can achieve the best possible expected return for a given level of risk. Specifically, it is the line on a graph representing the range of portfolios that maximize expected return at each level of portfolio risk.
Investments like bank accounts, bonds, and stocks all fall along a spectrum of risk and return; the efficient frontier helps to identify the most optimal portfolio mixes within this spectrum. Therefore, the answer to the multiple-choice question is B. efficient frontier.