Topic: Sequence of Tense,

Best Answer Explained in Below-:

The correct answer is **B) was washing**, and it is based on the context of the sentence. The structure of the sentence indicates a past action that was ongoing at the moment I arrived.

When we use "was washing," we employ the past continuous tense, which describes an action that was happening at a specific time in the past. In this case, the moment of arrival serves as that specific point in time. The sentence implies that he was in the process of washing his car when I showed up, suggesting an incomplete action that foreshadows my entrance into the scene.

Let’s briefly consider the other options:
- **A) washed** suggests a completed action, which does not fit because it doesn’t indicate that the action was ongoing when I arrived.
- **C) had washed** refers to a past perfect tense indicating an action completed before another past action, which again does not match the context of an ongoing action.
- **D) had been washing** also indicates an action that began in the past and continued up to another past point; however, it’s less immediate than "was washing" and doesn’t convey the same sense of the action being actively in progress at the arrival.

Thus, **"was washing"** accurately reflects the scenario, showing the action happening at a specific moment in the past.