I will be back in three days.为什么要有be 为什么不是I will back in three days.

i will be back in touch, “I will be back! soon i will be back in your arms I will be back in a couple of I will be back in a matter of hours. i will be back in touch,什么意思 I will be back in three days.为什么要有be 为什么不是I will back in three days. i will be back soon i will be coming back I will be back,from I will be back,We will be back i will be back为什么要be 找错 do you have enough students to carry the boxes?no,i think we need more tweo students.please wait thre.i will be back in two a half hours.the accident happened on 2007,february 5th I will be back in a minute.back不是动词吗?为什么前面还要加be呢? 英文翻译：I will be in Shanghai next week thru the 20th.这里的through I hope i will be back in a week.同意句是什么? He will be back in four days I don't know____he will be back.