Alzo il pollice quando la risposta è giusta.

Because Italian often leaves out subject pronouns when the verb ending already makes the subject clear.

• Alzo = I raise / I lift
• The -o ending shows it is first person singular

So Alzo il pollice naturally means I raise my thumb. You can add io if you want emphasis or contrast:

Io alzo il pollice, lui no.
I raise my thumb, not him.

Alzo is the first-person singular present tense of alzare, which means to raise, to lift, or to put up.

So:

• alzare = to raise
• alzo = I raise
• alzi = you raise
• alza = he/she raises

In this sentence, alzo il pollice literally means I raise the thumb, which in natural English is I raise my thumb.

Italian often uses the definite article with body parts when it is already obvious whose body part is meant.

So Italian prefers:

Alzo il pollice
rather than
Alzo il mio pollice

This is very common with body parts:

• Mi lavo le mani = I wash my hands
• Chiudo gli occhi = I close my eyes

Using mio is possible, but it usually sounds more emphatic than necessary.

Because giusta is an adjective, and in Italian adjectives usually agree in gender and number with the noun they describe.

• risposta is feminine singular
• so the adjective must also be feminine singular: giusta

Compare:

• il libro è giusto = the book is right/correct
• la risposta è giusta = the answer is correct

If the noun changes, the adjective changes too.

This is a very important spelling point:

• è with an accent = is
• e without an accent = and

So in this sentence:

la risposta è giusta = the answer is correct

If you wrote e instead, it would mean and, which would be wrong here.

Because Italian often uses the present tense in both parts of the sentence to talk about something that happens regularly, generally, or whenever a situation occurs.

So:

Alzo il pollice quando la risposta è giusta.

means something like:

• I raise my thumb when the answer is correct
• I raise my thumb whenever the answer is correct

This is a general or habitual statement, not just one single event happening right now.

Usually it sounds like a habit or a general rule.

Italian present tense can cover both:

• what happens now
• what happens regularly
• what is generally true

Here, because of quando and the context, the most natural reading is habitual:

Whenever the answer is correct, I raise my thumb.

If you wanted to make it clearly about this exact moment, context would usually do that.

Yes. That word order is completely natural.

Both of these are correct:

• Alzo il pollice quando la risposta è giusta.
• Quando la risposta è giusta, alzo il pollice.

The meaning is basically the same. The second version just puts the when-clause first, which may slightly emphasize the condition or timing.

Yes, it is understandable and natural in a literal sense: to raise the thumb.

Depending on context, Italian can also use other expressions for the gesture, such as:

• fare il pollice in su
• fare il gesto del pollice in su

But alzo il pollice is a clear and straightforward sentence, especially for describing the physical action.

Because in Italian, articles are used more often than in English.

Here:

• il pollice = the thumb
• la risposta = the answer

In English, we often say my thumb, but Italian commonly uses the with body parts when the owner is obvious.

With la risposta, the article is there because Italian normally needs an article before a noun in this kind of sentence. English sometimes sounds more natural without stressing the article, but Italian generally keeps it.

Yes. Giusto/giusta can mean:

• right
• correct
• fair
• appropriate

In this sentence, la risposta è giusta most naturally means:

• the answer is right
• the answer is correct

So giusta is a very common word for saying an answer is correct.