Can you understand it? is not 3rd person?

Hola Rosie L.

Thanks for your thoughtful question — it’s a really common point of confusion for learners.

You’re absolutely right that "you" is second person in English. However, in Spanish, when we use "usted", it’s the formal version of "you", and here's the key detail: it always uses third person singular verb forms. That’s just how Spanish grammar works, even though usted still means "you".

So in your quiz sentence:

the correct answer is comprende, not comprendes, because usted follows the same verb conjugation rules as él/ella (he/she).

If the sentence were informal — using tú — then yes, it would be:

I hope that helps make things clearer!

Let us know if you have more questions — you're doing great!

Un saludo

Silvia