单选题 All staff members in the research and development team have worked ______ hard throughout the year.

【正确答案】 A

【答案解析】[解析] 单词形态：副词
1．这是一道单词形态选择题，选项均为except的不同形式。
2．have worked和副词hard间应填入一个能修饰副词的词。而副词可以修饰副词，因此A为正确选项。