Fill in the blank with the correct option.

I _____ on Thursday. But on Thursday I had a terrible cold, so I decided to wait till Saturday.

was to have left

The correct answer is Option (2) → was to have left

The completed sentence is: I was to have left on Thursday. But on Thursday I had a terrible cold, so I decided to wait till Saturday.

This construction, "was/were to have + past participle", is used to express a planned or intended action in the past that did not happen.

• Intended Action: The plan was for the speaker to leave on Thursday.

• Preventing Circumstance: The plan was canceled or postponed because the speaker "had a terrible cold."

 Why the Other Options Are Incorrect: 

• am to leave (Present Intention): Expresses a current plan for the future (I am to leave tomorrow). It doesn't fit the past context of Thursday.

• would leave (Simple Conditional/Past Habit): Doesn't express the meaning of a failed past intention. (If I felt better, I would leave.)

• will be leaving (Future Continuous): Refers to an action ongoing in the future. (I will be leaving on Saturday.) It doesn't relate to the failed past plan on Thursday.