I am afraid I must be going与I am afraid I must go的区别

I am afraid I must be going与I am afraid I must go的区别 I am afraid I must be going It is getting late.I am afraid I must be going now. It is getting late. I am afraid I must be going now! It is getting late.I am afraid I must be going now!OK,______ 关于一个句子成分问题I am afraid I must be going.这个句子是个系表结构,那么 afraid 后 ---It's getting late .I am afraid I must be off now ----____ I am afraid I am afraid! I am afraid not. I afraid I'm must be going. be going 是什么时态 I am afraid ---(go)out alone