1.The man has to see a doctor. (改为否定句)
   The man ______ _____  to see a doctor.
2.They are staying there for three weeks.(对划线部分提问) 
   _____ _____ are they staying there?
3. Tom is 10 years old. Bob is 12 years old. (合并为一句)
     Tom is two years _____ _____  Bob.
4. Shanghai is the biggest city in China.(改为同义句)
    Shanghai is bigger than _____ _____ _____  in China.
5. Mary needs to take a bus to school.(改为一般疑问句)
   _____ Mary_____  to take a bus to school?