单选题 All senior staff members were supposed to attend the meeting in order to vote, ______ only three came.
【正确答案】 B
【答案解析】[解析] 词汇：连词
1．空格后接句子，D选项不是连词，因此排除。
2．原文意思是“所有的高级职员都应该参加但却只来了三个人”，连词but表示前后句的相反关系，因此B为正确选项。