No matter _____busy he is, he won't give up his hobby.      

He tried his best to solve the problem , ______difficult it was.     

句型转换。
1. Wang Xiao didn't go to school. She had a fever. (合并为一个复合句)
    Wang Xiao didn't go to school _____ she had a fever .
2. If you don't study hard, you won't pass the exam. (改为同义句)
   You won't pass the exam _____ you study hard.
3. I am 15. My brother is 13. (合并为一个复合句)
    I am two years older _____ my brother.
4. It's raining heavily, but I still go to school. (改为同义句)
    I still go to school _____ it's raining heavily.
5. It is three years since I joined the army. (改为完成时态)
    I have _____ the army for three years.

I know nothing about the news _____ my friend told me yesterday.

I am sleepy _____ I didn't sleep well last night.

—I'm not sure _________there are living things on the planets or not.
—Even scientists aren't sure about it.

—Did you have a good time at Alice's birthday party？
—Yes，indeed. It’s several years_____ I enjoyed myself so much.

It's quite common in Britain to Say "Thank you" to the drivers ________ people get off thebus.

_________ he is ill, _________ he goes to school.

"You can't have this football back _____ you promise  not to kick it at my cat again. " the old man said
angrily.