作业精灵老师示例：
S1：Is Liu Tao having a picnic with his parents？
S2：Yes, he is.
S1：Are Su Yang and Wang Bing drawing a picture？
S2：No, they aren't. They are flying a kite.
S1：Are the boys playing football？
S2：Yes, they are.
S1：Is Mike going boating with Nancy？
S2：No, he isn't. He is going cycling with Nancy.
