Which one of the following statements is correct?

a) If a stock is currently undervalued by the market, marginal investors will sell the stock.

b)If a stock is currently overvalued by the market, marginal investors will buy the stock.

c) If a stock is currently undervalued by the market, its expected return will increase as its price rises.

d) If a stock is currently overvalued by the market, its expected return will increase as its price drops.