一道英语选择题： He worked seven days a week, six of which until one clock. 这是定语从句吗？

【专家解说】：是非限制性定语从句 从句部分省略he worked，days 是先行词，which是引导词、在从句中作宾语， six of which是从句状语 完整的是：...,six of which he worked until one o'clock