my mother is keys are on the sofa 改为否定句

题目

my mother is keys are on the sofa 改为否定句
my mother is keys ___ ___on the sofa

答案

应该是My mother's keys are on the sofa..
否定句：My mother's keys are not on the sofa.(are就是一种助动词,直接在其后面加not构成一般疑问句,常缩写为aren't)