17 , the area's association with witchcraft dates back to Olmec times more than 2,000 years ago.
答案：(C) In fact
In fact（事實上）作插入語，用來強調、補充說明前文的巫術傳統其實可追溯到更早的奧爾梅克時期。In advance（事先）、In all（總共）、In sum（總之，通常用於總結段落）都不符合這裡「進一步強調事實」的語氣。
四個選項都是 In 開頭的片語，長得很像，容易混淆，你會憑哪個中文順挑一個。
這是邏輯勾環，線索一定要跨句才看得到。前一句說卡特馬科湖自前西班牙時期以來一直是另類醫療的中心；空格這一句說這個地區與巫術的關聯可以追溯到兩千多年前的奧爾梅克時期——時間往前推得更遠，是把前一句講的事再加強一層。這種「不只如此，其實還更……」用 In fact（事實上）。填進去讀成 In fact, the area's association with witchcraft dates back to Olmec times。鑑別度只有 30，但它本身不難：四個選項裡只有 In fact 是中學階段常見的轉承語，其餘三個本來就少見，各種程度的人都答得出來，題目自然分不出高低。
In advance（事先）講的是時間上的提前，與這一句的補充說明無關；In all（總計）用在把數量加總；In sum（總之）是收尾用的，但這一句是往下加、不是在收尾。
in fact（事實上）、as a matter of fact（事實上）、in advance（事先）、in all（總計）、in sum（總之）、date back to（追溯到）。
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.