①__________The balloon suddenly burst.  

② _________He burst into the room without knocking.  

③__________She burst into laughter when she heard she  was admitted into Beijing University.  =

    She    burst out laughing when she heard she was admitted    into Beijing University.  

④_______She burst into tears when she heard the    news that her boyfriend was missing in the  

   earthquake.= She burst out crying when she heard    the news that her boyfriend was missing in the 

   earthquake.