If you've ever seen the Sean Connery movie Medicine Man, 18 the annual convention of wizards and witches will be familiar to you.
答案：(C) then
If...then... 是固定的條件句型，then 承接 If 子句，引出「那麼……就會……」的結果。since（因為/自從）、so（所以，通常不與 if 連用）、though（雖然）都不符合這種標準條件句結構。
中文說「如果……那麼就……」，你會直覺想找一個「就」，而 so 的中文正是「所以」，很容易先被選走。
鑑別度高達 60，分開的是知不知道 if 子句後面該用哪一個字呼應。逗號前面已經有一個從屬連接詞 If 帶著子句，逗號後面是主要子句。英文不允許在同一組主從結構裡再放一個對等連接詞來連，所以 so 出局；since 與 though 都是從屬連接詞，放進去會變成兩個從屬子句、整句沒有主要子句，也不成立。剩下 then——它是副詞、不是連接詞，正好可以擺在主要子句前面呼應前面的 If，中文就是「那麼」。填進去讀成 If you've ever seen the movie Medicine Man, then the annual convention will be familiar to you。國中學過的「一個句子裡不能同時用 Although 和 but」是同一件事：中文的「雖然……但是……」「如果……所以……」到了英文只能留一邊。
so 是對等連接詞，中文的「所以」讓它看起來剛好，但它不能與句首的 If 並用；since（既然、自從）與 though（雖然）都是從屬連接詞，會讓整句缺少主要子句。
If ..., then ...（如果……那麼……）、Although ＋ 子句（雖然，主要子句不再加 but）、so（所以，對等連接詞）、though（雖然）、be familiar to somebody（為某人所熟悉）、convention（大會、集會）。
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.