Most witch doctors are guaranteed to be charlatans, not real doctors, who 20 some quick money from tourists.
答案：(A) go after
go after 在此是「追求、圖謀」：多數巫醫其實是江湖術士，圖的是觀光客口袋裡的快錢；turn down（拒絕）、give away（贈送、洩漏）、complain about（抱怨）語意都不合。
go after 你大概只熟它字面的具體動作——「追趕」（The dog went after the cat.），沒學過它可以用在抽象的目標上，表示「追求、圖謀」：go after a job（謀職）、go after the championship（力求奪冠）、go after money（貪圖金錢）。
先確認空格的身分。who 引導的是關係子句，who 是這個子句的主詞，空格就是它的動詞，所以四個選項都是動詞片語，句法這一關過不了篩——四個都塞得進去，只能靠語意分。接著要問一個關鍵問題：who 回指的是誰？往前找最近的名詞是 charlatans（江湖術士、騙子），不是 witch doctors；句子已經先說 Most witch doctors are guaranteed to be charlatans, not real doctors（多數巫醫肯定是騙子，不是真正的醫生），既然是騙子，後面接的動作自然是「撈錢」。先行詞認對了，語意方向就定了。驗算法：把整個關係子句還原成獨立句子唸一遍——They go after some quick money from tourists.（他們圖的是從觀光客身上快速撈一筆。）讀得通，方向就對。順帶把同源的 be after 一起記：be after sb 是「追捕、找某人麻煩」，學測考過 I don't believe God is after me（我不相信上帝在找我麻煩）。go after 與 be after 核心相同，都是「朝某個目標追過去」，差別在 go after 側重主動去謀取，be after 側重盯上某人。
三個都是動詞片語，錯在語意方向各不相同。turn down 是「拒絕」，方向與騙子的動機相反；要注意它還有「調低（音量、溫度）」一義，兩義都放不進本句。give away 是「贈送」或「洩漏（秘密）」，贈送與撈錢完全相反，洩漏則沒有受詞可對應。complain about 是「抱怨」，抱怨的對象通常是不滿的事，quick money 是他們想要的東西，不是抱怨的標的。
go after money／a job（追求金錢／謀職）、be after sb（追捕、找某人麻煩）、go for it（放手一搏）、turn down（拒絕；調低）、give away（贈送；洩漏）、quick money（快錢）、charlatan（江湖術士）。
Every year Catemaco, a small town in the south of Mexico, hosts the Annual Witch Gathering. Healers and witch doctors converge on this beautiful lakeside town in March to make their yearly trade. 16 since pre-Hispanic times, Lake Catemaco has been a centre for alternative medicine and strange treatments. 17, the area's association with witchcraft dates back to Olmec times more than 2,000 years ago.
If you've ever seen the Sean Connery movie Medicine Man, 18 the annual convention of wizards and witches will be familiar to you. 19, get prepared for the overwhelming attack of wizards and witches here.
Most witch doctors are guaranteed to be charlatans, not real doctors, who 20 some quick money from tourists. Yet, don't be surprised if the occasional remedy offered is effective.