说明
A. Even if B. Unless C. Now that D. As long as(全国英语专业四级,93-46)
核心问题
Unless ____ to speak, you should remain silent at the conference. A. invited B. inviting C. being invited D. having invited(上海高考,03-37) 答案为 A,但是 unless invited 是个什么结构呢?
词典解答
unless 引导的从句,如 if, when, while, until, although(though)引导的从句一样,其中的主语如与主句的主语相同,则有时会省略主语和谓语,尤其是当谓语动词是 be 时。上面的句子可以理解为: Unless you are invited to speak ... 见 once(conj.)², when²⁹, present participle¹¹。
unless/if... not 见 if... not
unmarked plurals(无标记复数) 见 people, police, cattle
unparalleled 见 very/much
unrestrictive relative clause (非限制性定语从句) 见 restrictive relative clause