1.This is not a pen.
2.Thatis not her book.
3.Are these my sisters?
There are not my sisters.
把陈述句改成否定句只要在动词后加上not；
把陈述句改成疑问句,如果句子中有be动词,只要把be动词提前,没有be动词的加助动词do/does（单数）放在句子开头