Learn Hardcore Indonesian: Anak perempuan itu diam di kelas karena ragu bertanya. - That girl is silent in class because she hesitates to ask.

itu is a demonstrative meaning that. After a noun phrase it often functions like English that/the to mark something specific/known. So anak perempuan itu can be that girl or the girl, depending on context. Use ini for this: anak perempuan ini.

Can itu come before the noun, like itu anak perempuan?

Yes. In colloquial speech itu can appear before a noun as a topic marker: Itu anak perempuan, diam di kelas... The neutral default for demonstratives is noun + itu/ini: anak perempuan itu/ini.

Does anak perempuan always mean girl? What about gadis, cewek, wanita?

anak perempuan: female child; neutral for girl (often pre-teen).
gadis: teenage/young unmarried girl; somewhat literary/formal.
cewek: informal/slang for girl.
wanita/perempuan (alone): woman; perempuan is common/neutral, wanita more formal.
In school contexts you may also hear siswi (female student) or murid perempuan.

Is diam a verb or an adjective here? Do we need adalah?

diam here is an intransitive verb meaning to be/keep quiet. Indonesian doesn’t use adalah in this kind of predicate. Examples:

Dia diam di kelas. = she kept quiet in class
Imperative: Diam! = be quiet As a descriptor it can mean quiet: anak yang diam = a quiet child

Could diam di kelas mean stay in class instead of be quiet in class?

Context decides. With a cause like karena ragu bertanya, diam means keep quiet. To say stay (remain) in class, prefer:

tetap di kelas
tidak keluar dari kelas berdiam di ... exists but is formal and often means to dwell/reside.

Should it be ragu untuk bertanya? Is leaving out untuk okay?

Both are fine:

ragu bertanya (colloquial/compact)
ragu untuk bertanya (a bit clearer/more formal) Reduplication adds emphasis: ragu-ragu (untuk) bertanya = hesitant to ask.

Why is there no pronoun after karena? Where did she go?

Indonesian often drops repeated subjects. karena ragu bertanya is understood as because she was hesitant to ask. You can include it: karena dia ragu untuk bertanya.

How do bertanya, tanya, menanyakan, and menanyai differ?

bertanya (intransitive): to ask (a question). Pattern: bertanya kepada [person] (tentang [topic]). Example: Dia bertanya kepada guru tentang PR.
tanya (root; casual verb/noun): to ask. Example: Dia tanya guru.
menanyakan [thing] (kepada [person]): to ask about something (thing as object). Example: Dia menanyakan PR kepada guru.
menanyai [person]: to question someone (person as object). Example: Guru menanyai murid.

What’s the nuance of ragu compared with malu or takut?

ragu: uncertain/hesitant (unsure whether/what to ask).
malu: shy/embarrassed.
takut: afraid (fear of consequences). Depending on the cause, you might say karena malu bertanya or karena takut bertanya.

Is di kelas the same as di dalam kelas?

They often overlap. di kelas is the default in class/in the classroom (during the lesson). di dalam kelas emphasizes physically inside the classroom or sounds a bit more formal.

How would you add emphasis like just kept quiet or kept on being quiet?

Common options:

diam saja di kelas = just kept quiet
tetap diam di kelas = remained quiet
hanya diam di kelas = only kept quiet

Could I say tidak bicara instead of diam? Any difference?

Yes. tidak bicara = did not speak; diam = stayed quiet/silent (often implies intentional silence). They overlap, but diam can feel more deliberate or complete.

How do you show past time in this sentence? There’s no tense marker.

Indonesian doesn’t inflect for tense. Add time words if needed, e.g., tadi (earlier), kemarin (yesterday), sudah (already). Example: Anak perempuan itu tadi diam di kelas karena ragu bertanya.

Any punctuation rule with karena?

If karena starts the sentence, use a comma after the cause: Karena ragu bertanya, anak perempuan itu diam di kelas. If the cause comes after the main clause (as in your sentence), a comma is typically not used.

How would you make it plural: the girls kept quiet...?

Mark the noun as plural:

Anak-anak perempuan itu diam di kelas karena ragu bertanya. You can also use a collective term (formal): Para siswi itu ...

Is kelas the room or the lesson? Would di kelasnya change the meaning?

kelas can mean the class session or the classroom; di kelas covers both. di kelasnya means in her/their class (possessive/context-specific), not just any class.