In the random walk hypothesis, the asset price follows a random walk, where there price in each period is completely uncorrelated with movements in prior periods. For prices that follow a random walk, which of the following assumptions needs to hold?

A. All existing information about the asset should be impounded in the current price.

B. Investors are unbiased in setting expectations (they don't consistently set them too high or too low).

C. Investors react instantaneously to new information.

D. The investor reaction to new information is unbiased.

E. All of the above.