回答

B
(1)
1. The girl (who/whom) my sister is playing with is Julie.
2. The girl with whom my sister is playing is Julie.
(2)
1. Math is the subject (which) I'm most interested in.
2. Math is the subject in which I'm most interested.
(3)
1. The CD (which) I'm listening to is Beth’s.
2. The CD to which I'm listening is Beth’s.
C
(1) (I found a bottle <in which there was) a letter>.
(2) (The woman <my brother got married to> is) a friend of his from childhood.
※get married to 人 人と結婚する

参考にしてください。

taka

文法的な説明を追加します。

(1) The girl is Julie. + My sister is playing with(前置詞) her(代名詞・目的格=Julie).
1. The girl (who/whom) my sister is playing [with] is Julie.
2. The girl [with whom] my sister is playing is Julie.
※her(代名詞・目的格) → who(m)(関係代名詞・目的格)に変えて、2つの文を一つにまとめたのが解答文:with+whomは省略できない
(2) Math is the subject. + I’m most interested [in](前置詞) it(代名詞・目的格=the subject).
1. Math is the subject (which) I’m most interested [in].
2. Math is the subject [in which] I’m most interested.
※it(代名詞・目的格) → which(関係代名詞・目的格)に変えて、2つの文を一つにまとめたのが解答文:in+whichは省略できない
(3) The CD is Beth’s. + I’m listening [to](前置詞) it(代名詞・目的格=the CD).
1. The CD (which) I’m listening [to] is Beth’s.
2. The CD [to which] I’m listening is Beth’s.
※it(代名詞・目的格) → which(関係代名詞・目的格)に変えて、2つの文を一つにまとめたのが解答文:to+whichは省略できない

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