l. midnight; when; cave
2. thousands; spring
3. reliable; what; about
4. determined; however
5. Once; up; mind
根据汉语提示完成句子，每空一词。 1. 当我们发现山洞时已是半夜时分。
l. midnight; when; cave
2. thousands; spring
3. reliable; what; about
4. determined; however
5. Once; up; mind