按要求改写句子。 
(1)同学们听课。（把句子写具体） 
                                                                                 
(2)我久久凝视着手中这面做工精致的五星红旗。（缩句） 
                                                                                  
(3)他从这么高的树上摔下来，怎么会不疼呢？（改为陈述句） 
                                                                                
(4)这个姑娘不漂亮，河伯不会满意的。（改为反问句）