一、根据句意和所给的中文提示，写出句子中的单词
1．How many ________ (国家) are there in the world?
2．I find it a little hard to learn ________ (俄语)．
3．The boy can work out the math problem ________ (容易地)．
4．Everyone loves the clean air and the warm________(阳光)．
5．He is an________(艺术家) and lots of people love him very much.
