答案：this my; it is; your pen
解析：仿照例子“Is this my coat? Yes, it is. It's your coat.”的结构，第一空应填“this my”构成“Is this my pen?”；第二空用“it is”回应一般疑问句；第三空根据语境填“your pen”表明“它是你的钢笔”。

答案：Is this my; it is; It's your book
解析：按照例子结构，问句为“Is this my book?”；肯定回答用“it is”；最后说明“它是你的书”，即“It's your book”。

答案：your mobile; it isn't; It's your mobile
解析：结合例子及语境，问句应是“Is this your mobile?”（这是你的手机吗？）；否定回答用“No, it isn't my mobile.”；最后说明“它是你的手机”，即“It's your mobile”。

答案：Is this; it isn't; It's your hat
解析：仿照例子，问句为“Is this your hat?”；否定回答用“it isn't”；最后表明“它是你的帽子”，即“It's your hat”。

答案：Whose is this; It's; bag
解析：依据例子，问句用“Whose is this bag?”（这是谁的书包？）；回答用“It's my bag.”（它是我的书包。）。

答案：Whose is this; It's; ruler
解析：按照例子结构，问句为“Whose is this ruler?”；回答是“It's my ruler.”。

答案：Whose is this; It's; pencil
解析：仿照例子，问句为“Whose is this pencil?”；回答为“It's my pencil.”。

答案：Whose is this; It's; mobile
解析：依据例子，问句是“Whose is this mobile?”；回答是“It's my mobile.”。