第 1 题 · 六级
The machine needs periodic checks, which the factory schedules every month.
核心词：periodic ˌpɪəriˈɒdɪk adj. 周期的，定期的
机器需要定期检查，工厂每月安排一次。
一般现在时主谓宾 + which 从句（频度）短语 a periodic check短语 periodic changes
The machine needs ___ checks, which the factory schedules every month.
第 2 题 · 六级
The company is on the brink of collapse, which the worried investors have long suspected.
核心词：brink brɪŋk n. 边缘
公司濒临倒闭，忧心忡忡的投资者们早就怀疑。
现在完成时主系表 + 介词短语 + which 从句（现在完成 + 副词）短语 on the brink of短语 the brink of war
The company is on the ___ of collapse, which the worried investors have long suspected.
第 3 题 · 六级
The compression of the file saves space, which the engineer had explained to the team.
核心词：compression kəmˈpreʃn n. 压缩
压缩文件节省空间，工程师已向团队解释过。
过去完成时主谓宾 + 介词短语 + which 从句（过去完成 + explain to）短语 data compression短语 a compression ratio
The ___ of the file saves space, which the engineer had explained to the team.
