The graph below shows what happens to standard deviation of returns (portfolio risk) as more and more stocks are randomly added to a portfolio.

Which of the following statements best describes the implication of the above graph.

Group of answer choices

a. Portfolio risk is decreasing because market risk is declining

b. As more securities are added portfolio risk will eventually become 0.

c. Portfolio risk is decreasing because unsystematic risk is being diversified away.

d. On average stocks are negatively correlated with each other