○　正解です。

'interested in' is an adjective (形容詞). It describes how a person feels. (興味を持っている)
For example : I'm interested in music.

'interesting' can also be an adjective. It describes something (or someone) that makes people feel interested. (興味を引き起こす)
For example : Music is interesting.

'interest' is a verb (動詞) and is used as follows.
Music interests me.

Some other verbs/adjectives that follow the same pattern are :
(興奮した) excited/exciting/excite
(退屈した) bored/boring/bore
(疲れた又は飽きた) tired/tiring/tired
(ぎょっとした) frightened/frightening/frighten