第 1 题 · 六级
The engineer checked the valve before the test, which had to control the flow of gas precisely.
核心词：valve vælv n. 阀门
工程师在测试前检查了阀门，阀门必须精确控制气体流量。
一般过去时主谓宾 + 时间状语 + which 从句（have to + 副词）短语 a safety valve短语 turn the valve
The engineer checked the ___ before the test, which had to control the flow of gas precisely.
第 2 题 · 六级
She is still working on her thesis, which the professor expects to receive before the holiday.
核心词：thesis ˈθiːsɪs n. 论文；论点
她还在写论文，教授希望在假期前收到它。
现在进行时现在进行时 + 介词短语 + which 从句 + expect to do短语 write a thesis短语 a graduation thesis
She is still working on her ___, which the professor expects to receive before the holiday.
第 3 题 · 六级
The divers completed the certification for open water, which allowed them to dive without an instructor.
核心词：certification ˌsɜːtɪfɪˈkeɪʃn n. 证明，认证
潜水员完成了开放水域的资格认证，这让他们可以无教练独自潜水。
一般过去时主谓宾 + 介词短语 + which 从句 + allow sb to do短语 a certification exam短语 obtain certification
The divers completed the ___ for open water, which allowed them to dive without an instructor.
