按要求改写下列句子，每空一词。 1. Open the door, please. (改为否定句) ___   _ open the door, please. 2. I can see a cup of coffee on the table. (对画线部分提问) _ __   _ can you __   __ on the table? 3. There are thirty students on the playground. (对画线部分提问) How _ ____ _ ______ are there on the playground? 4. There are some birds in the tree. (改为一般疑问句) _ __    _ there birds in the tree? 5. They often play basketball on the playground .(对画线部分提问) ___   _ ______ they often _ _    __ basketball?