Is this a pencil case?能这样写吗?

This is a pencil box.对a pencil box 提问 This is a pencil box.(对” a pencil box”提问 ) this is a pencil 改为一般疑问句 this is a pencil改为复数句 --- () is this?--It's a pencil 我的CAS statement上面写着THIS IS NOT A CAS STATEMENT,谁知道这是不是真正的CAS? What is this?----This is a pencil sharpener改错 this is your pencil is,too,that,pencil,my,and) (is,case,yellow,this,a,pencil(is,too,that,pencil,my,and) (is,case,yellow,this,a,pencil)连词成句 This is a pen and ____ is a pencil. This pencil is 18cm.That pencil is 20cmThis pencil is a ___ ____ than that one This is a pencil and a pen还是These are a pencil and a pen what a( )this pencil? This is a pen,and ____is a pencil over there This is my a pencil sharpener in English.对a pencil sharpener 提问 This is a pencil sharpener.(改为一般疑问句) This is a pencil box 改为一般疑问句 is this a pen ___ your pencil case