Which statement(s) about galaxy groups is/are true? 
 Choose one or more: 
 A. Galaxy mergers in groups are not known to have ever happened 
 B. Galaxies in a group are all moving away from each other. 
 C. Interactions between massive and less-massive galaxies affect only the smaller galaxies. 
 D. Tidal streams can result from galaxy interactions. 
 E. The largest galaxies tend to have satellite galaxies.