1. It's very hard to work out the math problem. (同义句)  
     ______ the math problem is very har.
2. I would like to come to China for my vacation. (改为一般疑问句)  
     ______ like to come to China for ______ vacation.
3. How about taking him to the Ming Tombs? (作肯定回答)  
    ______ ______!
4. Maria has to finish her homework first. (否定句)  
    Maria ______ ______ to finish her homework first.
5. We can explore the graves of ancient Chinese emperors. (就划线部分提问)  
     ______ ______ we explore?