单选题
It is the responsibility of agents at the airline's check-in counters to have baggage tags on hand for travelers who ______them.
【正确答案】
B
【答案解析】解析：关系代词作主语的定语从句“who______them”中缺少谓语动词，故动词(B)和(C)为备选答案。主格关系代词who所代替的先行词travelers为复数形式，所以谓语动词要用原形，故(B)request为正确答案。