Using a modal auxiliary:I’m sure you have left your phone in you

Using a modal auxiliary:
I’m sure you have left your phone in your office.
【正确答案】：You must have left your phone in your office.
【题目解析】：Must表示推断，指具有较大的可能性。后接完成式，用来表示谈论已发生的情况，意为必定、很可能。