Is this your back pack ?

这是你的书包吗？Is this your backpack?
zhè shì nǐ de shū bāo ma ？ 
这是我的书包 This is my backpack
zhè shì wǒ de shū bāo 
那是你的铅笔吗？Is that your pencil?
nà shì nǐ de qiān bǐ ma ？ 
那不是我的铅笔 that is not my pencil
nà bù shì wǒ de qiān bǐ

Review vocabulary on Quizlet:
https://quizlet.com/165451219/flashcards/starred (Stationary)

https://quizlet.com/165449196/flashcards (I, my; you, your, this is。。。)