A andom walk occurs when______.A.stock price changes are random but predictableB.stock

A "random walk" occurs when______.

A．stock price changes are random but predictable

B．stock prices respond slowly to both new and old information

C．future price changes are uncorrelated with past price changes

D．past information is useful in predicting future prices

请帮忙给出正确答案和分析，谢谢！