根据汉语完成句子。 

1. 请保持室内整洁。  

    Please __         __ the room ___          _.  

2. 你对抽烟怎么看？    

    How do you feel                ________?  

3. 坚硬的座位使顾客感到不舒服。   

    Hard seats         ___ customers _______  _             . 

4. 不要使这个男孩长时间做作业。    

    Don't                 the boy ____         his homework for long.  

5. 他们必须知道如何制作食物。    

   They have to know                             _  _______ food.