Answer:
sell the stock which will drive it's expected return even lower.
Explanation:
An investor wants to be compensated for the risk undertaken in the form of return. When investors believe that a stock is not providing sufficient return, such stocks would be sold by the investor.
When a stock is not performing well i.e it's current market price goes down, all the investors holding that stock will sell it , leading to it's market price going further down.
Since the market price goes further down, the expected return on such a stock would further decline.