They may also pretend to be 14 customers, arguing with a salesperson without a good reason.
答案：(A) difficult
difficult 形容人時是「難相處的、難搞的」，a difficult customer 即「奧客」，與後面的分詞構句 arguing with a salesperson without a good reason 完全吻合；potential（潛在的）、constant（持續不斷的）、anonymous（匿名的）都不合。
答對率 25%。
difficult 你只記得「困難的」，用來形容事情（a difficult question）；形容「人」時它會轉彎，變成「難相處的、難搞的」——a difficult customer 就是「奧客」，a difficult child 是「難帶的孩子」。
空格後緊接 arguing with a salesperson without a good reason（無緣無故就跟店員起爭執），這個分詞構句正是在解釋「difficult 的顧客」長什麼樣。「看到空格後接逗號加分詞或同位語，先讀那一段，答案常常就在裡面。」
easy（容易的／隨和的，an easy person to work with）、hard（困難的／嚴厲的，be hard on sb）、tough（艱難的／強悍的）、mean（吝嗇的、刻薄的）。看到熟悉的形容詞去修飾人，先想它有沒有第二個意思。
a difficult customer（難搞的顧客、奧客）、a difficult child（難帶的孩子）、a regular customer（常客）、a potential customer（潛在顧客）、mystery shopper（神祕客）。
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.