Why does a company’s stock price generally go up on a good announcement, then retreats days after?

I understand that many institutional investors buy lots of shares the day a company announces good news. Usually, the next day, the stock price retreats a little, only to eventually go back up. Why does this happen?

Which of the following activities would generally not be included in the social audit of a business?

A.Support for higher education, the arts, and nonprofit groups.
B.Employee-related activities.
C.Comparisons of charitable donations versus the donations of other firms.
D.Consumer activities such as product safety, honest advertising, and fair pricing.