Sometimes referred to as secret shoppers, mystery shoppers 11 regular customers to purchase items, eat in restaurants, make inquiries, or return items.
答案：(B) pose as
【句型】pose as 字詞搭配「假扮成」，表示神秘客「假扮成」一般顧客去購買商品；call for（需要）、attend to（處理）、engage in（從事）都不合。
pose 在你腦中的第一個畫面多半是拍照時「擺姿勢」（pose for a photo），所以看到 pose as 會覺得跟句子搭不上。pose as sb 是另一個常考用法：假扮成、冒充某種身分——擺出那個身分的樣子給別人看，其實和「擺姿勢」是同一個核心概念，只是這裡擺的是身分不是姿勢。
主詞是 mystery shoppers（神秘客），前一句 Sometimes referred to as secret shoppers 已經強調「祕密」。空格後是 regular customers to purchase items（一般顧客，去買東西）——神秘客的工作正是不表明身分、裝成普通客人。再往下 They may also pretend to be ___ customers，pretend to be 就是 pose as 的同義說法，文章自己給了對照。
call for 是「需要、要求」（The situation calls for caution. 情況需要謹慎）；attend to 是「照料、處理」，注意 attend a meeting（出席會議）少了 to 才是「參加」，差一個 to 意思就變了；engage in 是「從事（某活動）」，後面接活動不接身分。
pose as sb（假扮成某人）、pose a threat to sb／sth（對……構成威脅）、pose a problem for sb（為……帶來問題）、pretend to be（假裝是）、call for（需要、要求）、attend to sb（照料某人）、attend a meeting（出席會議）、engage in sth（從事……）。
Mystery shoppers are paid consumers who are hired to shop in stores and collect data. They are sent to a wide variety of service-based businesses, including stores, restaurants, and banks—potentially anywhere customers are served. Sometimes referred to as secret shoppers, mystery shoppers 11 regular customers to purchase items, eat in restaurants, make inquiries, or return items.
They grade and report on the quality of products, customer service, and environment of the stores 12 they are assigned. When evaluating a business, mystery shoppers have to follow certain standard procedures to avoid 13 . They are often given a checklist that provides directions on what to observe or look out for to ensure consistency.
Sometimes these shoppers collect data about their "normal" observations, such as cleanliness of the store or timeliness of the service. They may also pretend to be 14 customers, arguing with a salesperson without a good reason.
With the data they collect, mystery shoppers can identify areas for 15 and thereby help enhance the quality of products and services. In this way, these secret shoppers may help a business gain a competitive edge.