I left m at home

I left m at home I'm sorry,I left my homework at home I left\forgOt my book at home. i （left） it at home I left my wallet at home ----I'm sorry,Mr Li.I left my exersise book at home. I left mine at home.为什么这里要用left ——I'm terriblt sorry for having left your comic book at home Hello; I'M At Home i'm staying at home I am a( )I have left my key at home 请问是I forget my homework at home.还是I left my homework at home