I'm afraid I must be going .这句话为什么用被动语态?

I'm afraid I must be going .这句话为什么用被动语态? I am afraid I must be going I afraid I'm must be going. be going 是什么时态 I am afraid I must be going与I am afraid I must go的区别 --It‘s getting late.I'm afraid I must be going now.--OK.____ -It's geting late.I'm afraid I must be going now. -Ok.______ It's geting late.I'm afraid I must be going now --it's getting late.I'm afraid I must be going now. 1:I’m afraid I must be going now.2.Sit down,please.3.Heall!J 初二被动语态Must i finish the homework改为被动语态是Must the homework be i must be paid for this 这句怎么翻译啊?看起来是被动语态 I’m afraid you must