阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空。
I have some great friends at summer camp. They can all do different ____ (thing). This is Helen. She's good at ____ (musical). She can sing, and she can play ____ piano. Oh, she's a ____ (greatly) dancer, too. But she can't cook. And she can't play the guitar. Tom is ____ (real) cool. He is from America. He can speak Chinese well, and he can ride a motorbike. He can't play the piano ____ the guitar, but he can sing·
Then this is ____ (I) sister Alice. She can run really fast, and she can ____ (player) basketball and soccer. She can ride a bike. But she can't ride a motorbike.
Charles ____ (do) well in sports. He can swim, and play tennis and basketball. He can run fast, too. ____ he can't cook. Julie can speak Chinese, and she can cook, too.
2Fe+3CO2 ,该反应中的还原剂是（）