Translation: The temple was very beautiful.
- Explanation: The time marker is 'きのう' (yesterday), indicating the temple visit is a completed past event. Therefore, the adjective 'きれい' (na-adjective: beautiful/clean) must be conjugated into the past tense. The past polite form is 'きれいでした'.
- Conjugation comparison of choices:
- きれいでした (Past positive - Correct)
- きれいです (Present positive)
- きれいじゃないです / きれいじゃありません (Present negative)