Which of the following statements is false?

a) when we combine many stocks in a large portfolio, the firm-specific risks for each stock will average out and be diversified.

b) the risk that the evolution of resistance can render all coivd-19 vaccine under clinical trial ineffective is a diversifiable risk.

c) the risk premium for diversifiable risk is zero.

d) fluctuations of a stock's returns that are due to industry-specific news are diversifiable risks.

e)none of the above