Jawaban:

Dan: Hey, Margo.

Margo: Hi.

Dan: Do you know the boy who's standing in front of the library?

Margo: The one with a flannel?

Dan: Yes.

Margo: I believe he's the new student.

Dan: The new student?

Margo: Yes, Jimmy's brother.

Dan: Who's Jimmy?

Margo: The boy whose hair always so messy. He sits next to me in class.

Dan: Oh... I see.

Preposition yg digunakan: In front of, next to

Adjective Clause yg digunakan: who, whose

Penjelasan:

krn kurang tau pake informal atau formal dialognya, aku buat yg informal aja ya. Ini artinya:

Dan: Hai, Margo

Margo: Hai.

Dan: Kamu tau ga siapa cowok yg berdiri di depan perpus?

Margo: Ah yg pake jaket flannel?

Dan: Iya.

Margo: Kayaknya murid baru deh.

Dan: Murid baru?

Margo: Iya, adiknya Jimmy.

Dan: Jimmy siapa?

Margo: Cowok yg rambutnya selalu berantakan. Yg duduk disebelahku di kelas.

Dan: Ah... oke oke.

semoga membantu :)