Scientists also report that the category 15 the person belongs (family, close friends, etc.) is far more influential in causing a mix-up than any phonetic similarity between names.
答案：(B) to which
【關係代名詞】to which 引導形容詞子句修飾 category，還原句意為 the person belongs to the category，介系詞 to 須提前置於 which 之前。by whom（被誰）、in that（因為）、for what（為了什麼）皆不符合此處 belong to 的固定搭配及句構。
本題大考中心未公布逐題答對率，以下不談數據，只談觀念。
四個都是「介系詞加關係詞」的組合，形態很像，很容易憑語感挑；by whom 因為 the person 是人，看起來特別合理。
這一類題只有一條路走得通：把關係子句還原成一個獨立的句子，看缺的是哪一塊。原句是 the category ______ the person belongs（那個人所屬的 ______ 類別），還原成 The person belongs to the category.（那個人屬於這個類別）。belong 是不及物動詞，後面一定要接 to 才帶得出「屬於什麼」，belong to 是課本教到爛的固定組合，所以介系詞確定是 to。再看先行詞：the category 是東西不是人，關係代名詞用 which。合起來就是 to which。判準壓成一句話：先還原成完整句子，看動詞需要哪個介系詞、先行詞是人還是物，兩件事分開決定，就不會在四個組合之間繞圈子。
by whom 的 whom 指人，但先行詞是 the category（類別），對不上；而且 belong 也不配 by。in that 是連接詞，意思是「因為、在於」（It is a good plan in that it saves time），後面要接完整的子句，不是回頭修飾前面的名詞。for what 不成立——前面已經有先行詞 the category 時就不能用 what，得改用 which 或 that，這是 what 的鐵律：它自己已經含著先行詞，前面不能再站一個名詞。
belong to（屬於）、介系詞 ＋ which（回頭修飾前面的名詞）、the category to which ...（……所屬的類別）、in that（因為、在於）、influential（有影響力的）、phonetic similarity（語音上的相似）
"Anne! Jo! I mean, Max!" Mothers often mix up their children's names, but studies show that moms are not the only ones who make this mistake. 11 name phenomenon turns out to be very common. Almost everyone sometimes mixes up the names of their family and friends.
The phenomenon is called a "cognitive glitch" by researchers in the field of cognitive science. It is not caused by a bad memory or by aging processes that affect brain functioning. It is simply a result of the way our brain 12 those we love.
When our brain is attempting to retrieve a name so that we can say it, it is likely that another name in the same group will come to our lips 13 the one we meant to say. That is because in order to find the name we are looking for, we are essentially 14 the whole set of names in that group, which includes all our beloved family members. Scientists also report that the category 15 the person belongs (family, close friends, etc.) is far more influential in causing a mix-up than any phonetic similarity between names. Names that sound alike do not usually trigger the mix-up.
Isn't it great to know that when you call others by the wrong name, it is evidence of your love for them all?