题目类型：
填空题
题目内容
根据题干要求填空
With a relative pronoun or a relative adverb:
The ten-year-old American boy swam to and from a remote island within an hour,______was a great achievement for a kid of his age.
With a relative pronoun or a relative adverb:
The ten-year-old American boy swam to and from a remote island within an hour,______was a great achievement for a kid of his age.
正确答案
which