eng question

當然Pride and Prejudice的作者絕對沒有錯，

marrying正如Garlic兄所說，是動名詞(gerund)（它有動詞性質，但卻作名詞用）

動名詞很特別，它有它意思上的主詞，而那主詞卻要用所有格(possessive case)，但若和主要句子的主詞相同時，則可省略，如：

He insisted on my going there.(他堅持要我去那兒）
He insisted on going there.（他堅持要去那兒）
Would you mind opening the window？（請你把窗打開，好嗎？）
Would you mind my opening the window?（我將窗門打開，你介意嗎？）

marrying（在這裏意思是指：嫁或娶），其後可直接有受詞，
但若用marriage則要用to，或with帶出受詞

所以，你大可寫：

I'm thinking of his marriage to one of them

希望幫到你！

如果沒估錯你的意思是
我正思想他是會跟兩人中其中一個結婚。

這兩句都錯，第一句錯了一個字
his → him才對
I'm thinking of him marrying one of them.
其實這句的結構是
I'm thinking of "something"
這"something"是
He is marrying one of them
結合這兩組句而成的，所以有點縮減的文法技巧在裏面的。

第二句改的部份marriage並不是這種詞性的用法，如要改為marriage則全句的其他字也要改
I'm thinking of his marriage being to one of them.
這句其實是結合兩部份而成
I'm thinking of his marriage
his marriage is to one of them 這不是常見的寫法，但就著原句意思他從兩人中選擇一成為他的結緍對象，但這句由於用marriage便要是已成事實的陳述才會這樣寫，如果他還未結婚，則必要用第一句因為marrying可以是暗示他的意圖而不是已成事實的marriage.

留意就算是類同意思的字並不一定可以轉換的，除了文法外，背後可能還有些文化因素決定一句如何寫/講的。

I'm thinking of his marrying one of them. (correct)

I'm thinking of his marriage one of them. (incorrect)

I'm thinking of his marriage with one of them. (correct)

Marrying is a gerund, i.e., a verbal noun, which is a noun depicting some kind of action. A gerund has some of the properties of a verb, one of them being that it can take an object if the verb form is transitive.

I thought that he should marry one of the grils.