They are necessary when the customer is 13 or when the vendor has done all that can reasonably or legally be expected.
答案：(A) at fault
at fault（有過錯的／出差錯的）表示當顧客本身理虧或有疏失，或是廠商已盡合理合法責任時，就應發出拒絕調整的訊息；on call／in tears／off guard 均不符合此處語意。
四個選項都是「介系詞加名詞」的片語，中文都能說成「處於某種狀態」，你會覺得每一個好像都放得進去。
答對率四成一。四個選項都是介系詞片語、都能接在 be 動詞後面當補語，形態上刷不掉，這一格考的是認不認得這幾個片語各自的意思。先確認整句在講什麼：Adjustment refusals are necessary when the customer is ______ or when the vendor has done all that can reasonably or legally be expected.（在什麼情況下必須拒絕客戶的要求）。這裡有一個 or 連著兩個 when 子句，要先看清楚它連的是哪兩樣——是兩種「該拒絕的情況」；後面那一種寫得很清楚：賣方該做的都已經做到了。既然兩種情況並列，前面那一種就該是「錯不在賣方」的另一半，也就是客戶自己有問題。at fault 正是「有過失、該負責任」，填進去讀成 when the customer is at fault（當過錯在客戶這一方時）。
on call（隨時待命）用在醫師、工程師這類職務上，客戶不會待命；in tears（淚流滿面）講的是情緒，與該不該拒絕無關；off guard（沒有防備）通常出現在 catch somebody off guard（趁人不備）這個組合裡，單獨接在 the customer is 後面很少這樣用。三個都是介系詞片語，形態吻合，容易被順手選走。
at fault（有過失、該負責）、catch somebody off guard（讓某人措手不及）、on call（隨時待命）、in tears（淚流滿面）、reasonably（合理地）、legally（在法律上、依法）。
Handling customer claims is a common task for most business firms. These claims include requests to exchange merchandise, requests for refunds, requests that work 11, and other requests for adjustments. Most of these claims are approved because they are legitimate.
However, some requests for adjustment must be 12, and an adjustment refusal message must be sent. Adjustment refusals are negative messages for the customer. They are necessary when the customer is 13 or when the vendor has done all that can reasonably or legally be expected.
An adjustment refusal message requires your best communication skills 14 it is bad news to the receiver. You have to refuse the claim and retain the customer 15. You may refuse the request for adjustment and even try to sell the customer more merchandise or service. All this is happening when the customer is probably angry, disappointed, or inconvenienced.