U were watching tv when i was preparing for my exam.

Answer:

Explanation:
The correct answer is option 'C' - "I was preparing".

When we use the past continuous tense, we are describing an action that was happening at a specific time in the past. In this case, the action of preparing for the exam was happening while you were watching TV.

Past Continuous Tense:
The past continuous tense is formed using the past tense of the verb "to be" (was/were) and the present participle form of the main verb (preparing).

Usage of "Was preparing":
In this context, "I was preparing" indicates that the action of preparing for the exam was ongoing in the past, specifically when you were watching TV. It suggests that you started preparing before the moment you were watching TV and continued to do so during that time.

Contrast with other options:
- Option 'A' - "I prepared" indicates that you finished preparing for the exam before you started watching TV. It does not convey the idea that the action of preparing was ongoing at the same time as watching TV.
- Option 'B' - "I am preparing" indicates that you are currently in the process of preparing for the exam. This does not align with the past context of the sentence.

Therefore, option 'C' - "I was preparing" is the correct answer as it accurately reflects the past continuous tense and describes the ongoing action of preparing for the exam while you were watching TV.