Which of the following statements is true of systematic risk?

a. Systematic risk is reduced by constructing a diversified portfolio and depends on the firm's business and financial risk.

b. Systematic risk is the tendency for a stock's return and the return on the market to move together and is reduced by constructing a diversified portfolio.

c. Systematic risk is the tendency for a stock's return and the return on the market to move together and is measured by beta coefficients.

d. Systematic risk is reduced by constructing a diversified portfolio and is measured by beta coefficients.