Why do mergers cluster in time, causing merger waves? (Select all the choices that apply.) A. It is clear that merger activity is much greater during economic expansions than during contractions and that merger activity strongly correlates with bull markets. B. Many of the same technological and economic conditions that lead to bull markets also motivate managers to reshuffle assets through merger and acquisitions. C. Generally, a combination of forces usually only present during strong economic expansions drive merger activity to peak levels. D. Merger mania is caused by the fear that only big companies survive in a time of increasing merger activity