Am I a teacher?(直接将be动词提前）
I am not a teacher.（在be动词后加not）
Can he go to school on foot?(将情态动词can提前）
He can't go to school on foot.(情态动词后加not)
Does she do some swimming in the lake?(借助组动词does,但是实意动词要还原成原形）
She doesn't do some swimming in the lake.（也是借助助动词does,再在后面加not)