Step 1: Determine the type of feeling or situation that the interjection must express. In this context, the interjection should convey a mild mistake, slip, or small accident made unintentionally.
Step 2: Evaluate the meaning and usage of each option:
- Oops — commonly used when someone makes a sudden or minor error or accident, so it fits the situation well.
- Aww — expresses sympathy, affection, or disappointment, not a mistake.
- Phew — is used to show relief after tension or difficulty.
- Ah — indicates realization or understanding.
Step 3: Since Oops correctly expresses a mild mistake or accident, the correct answer is (A).