求翻譯：Facebook says it is the world’s largest social network, with 175 million members. But in the United States, most members are still relatively young; Facebook offers advertisers a target of 54.4 million members of all ages. But if an advertiser wants to narrow its target audience to those 25 or older, the number drops t是什么意思？

待解決 懸賞分：1 - 離問題結(jié)束還有