过去完成时的用法 — 英语词汇题
题目
根据句意，用括号内动词的适当形式（过去完成时或一般过去时）填空，每空一词。 Before Ling accepted the invitation to give a speech at the Youth Science Forum, she ______ (finish) all the experiments that other researchers ______ (not even begin) to try, which made her achievement truly remarkable.