Translation: Hokkaido was very cold.
- Explanation: The trip occurred '先週' (last week), establishing a past context. The adjective 'さむい' (cold - I-adjective) must be conjugated into the past tense before 'でした' in standard writing, or simply used as 'さむかったです' (or plain past 'さむかった' before 'でした'). The plain past form is 'さむかった'.
- Choices analysis:
- さむかった (Past positive - Correct)
- さむい (Present positive)
- さむくて (Te-form)
- さむくない (Present negative)