オリジナル問題
次の英文を動名詞を使って書きかえよ。
I'm proud that he is interested in it.
選択肢1 I'm proud of his being interested in it. 
選択肢2 I'm proud of he being interested in it.
選択肢3 I'm proud of he interested in it. 
選択肢4 I'm proud of his interesting in it.