Can someone explain why (a) is correct?

Correct Answer You Answered 0/1 pts Question 2 Which one of the following events would be included in the expected return on Sussex stock? This morning, Sussex confirmed that its CEO is retiring at the end of the year as was anticipated The labor union representing Sussex's employees unexpectedly called a strike O The board of directors made an unprecedented decision to give sizeable bonuses to the firm's internal auditors for their efforts in uncovering wasteful spending The chief financial officer of Sussex unexpectedly resigned The price of Sussex stock suddenly declined in value because researchers accidentally discovered that one of the firm's products can be toxic to household pets