The key the string was put into the door to stop the kite .A. tie to;flying awayB. tying

问题补充：

The key the string was put into the door to stop the kite .

A. tie to;flying away

B. tying to;fly away

C. tied to;flying away

D. tied to;fly away

答案：

A. tie to;flying away

B. tying to;fly away

(答案→)C. tied to;flying away

D. tied to;fly away

解析：考查非谓语动词和固定短语。The key和动词tie to之间是动宾关系，所以要用过去分词形式，排除A,B；stop the kite 用的是阻止某人做某事结构，stop…(from)doing…结构。所以选C。