按要求改写句子。(20分)
（1）Students enjoy themselves in summer.(改为同义句)
Students________________  ________ ________ in summer.
（2）He is planting rice. (改为一般疑问句)
________he________rice?
（3）Is she making a sandcastle? (作肯定回答)
________，she________.
（4）She is looking for the shells.(改为否定句)
She________ ________for the shells.