I lent my new book to a friend. [Syntax]

The correct answer is "ほん" (hon). This noun means "book." It is the direct object of the verb "かしました" (kashimashita, lent) and is modified by "わたしの" (watashi no, my) and "あたらしい" (atarashii, new). It must be followed by the direct object particle "を." "わたしの" is a possessive phrase. "あたらしい" is an adjective meaning "new." Both modify "ほん." "を" is the direct object particle, which always comes after the noun it marks.

正解は「ほん」です。「ほん」は動詞「かしました」の直接の目的語となる名詞で、「わたしの」と「あたらしい」によって修飾されます。その後に助詞の「を」が来ます。「わたしの」は所有を表す表現です。「あたらしい」は形容詞です。「を」は目的語を示す助詞で、名詞の後に続きます。