Preguntaron por el sexo de la persona.

Preguntaron is the preterite, 3rd person plural form of preguntar.

• preguntaron = they asked
• preguntó = he/she/it asked
• preguntaban = they were asking / used to ask

In this sentence, preguntaron presents the action as a completed event in the past: They asked about the person’s sex.

Spanish often uses the 3rd person plural with no stated subject when the speaker means they in a vague or unspecified way, similar to English they asked when we do not say exactly who they are.

Spanish often omits subject pronouns when the verb ending already shows who is doing the action.

Here, preguntaron already tells us the subject is they. So ellos/ellas is unnecessary unless the speaker wants emphasis or contrast.

This is very natural in Spanish:

• Preguntaron por el sexo de la persona.
• literally: They asked about the sex of the person.

English usually needs a subject, but Spanish often does not.

Because preguntar por means to ask about or to inquire about something.

Compare:

• Preguntar algo = to ask something
  
  • Preguntó la hora. = He asked the time.
• Preguntar por algo / alguien = to ask about something / someone
  
  • Preguntaron por el sexo de la persona. = They asked about the person’s sex.

So in this sentence, por is required because the idea is not asking a direct question word-for-word, but asking about a topic.

Here, por does not mean for in the usual English sense. In this structure, preguntar por is a fixed expression meaning:

• to ask about
• to inquire about

So por el sexo means about the sex, not for the sex.

This is one of those cases where translating the preposition word-for-word is not very helpful; it is better to learn preguntar por as a unit.

Spanish often uses the definite article more than English does.

So el sexo de la persona literally means the sex of the person, even though in English we might naturally say the person’s sex.

The article el is included because Spanish commonly uses articles before nouns in this kind of general or specific reference. Omitting it here would sound unnatural.

In this sentence, sexo most naturally means biological sex or registered sex.

In modern usage, Spanish often distinguishes:

• sexo = sex
• género = gender

So if someone asked about how the person identifies socially or psychologically, género might be more appropriate in some contexts. But sexo de la persona normally refers to sex, especially in medical, legal, or administrative contexts.

Spanish often prefers de + noun when the possessor needs to be clear.

• el sexo de la persona = the person’s sex
• su sexo = his/her/their sex

The problem with su sexo is that su can be ambiguous:

• his
• her
• its
• their
• your formal

So de la persona makes it explicit: it is the sex of the person.

Because persona is a grammatically feminine noun in Spanish, regardless of the actual sex of the individual.

So you say:

• la persona
• esa persona
• una persona amable

even if the person is male.

This is a very common point for English speakers: grammatical gender and real-world sex are not always the same thing.

No. In this sentence, it clearly means They asked about the person’s sex.

Why? Because of the structure:

• preguntar por + noun = to ask about + noun

If someone wanted to say to ask for something, Spanish would usually use another verb or a different structure, such as:

• pedir = to ask for / request

So preguntaron por el sexo de la persona is about requesting information, not asking to obtain something.

Yes. La persona is singular, so the sentence refers to one person.

• de la persona = of the person

If it were plural, it would be:

• Preguntaron por el sexo de las personas.
• They asked about the sex of the people.

So the sentence is specifically about one individual.

Yes, but it changes the structure slightly.

• Preguntaron por el sexo de la persona.
  = They asked about the person’s sex.

• Preguntaron cuál era el sexo de la persona.
  = They asked what the person’s sex was.

The first version is a little more compact and treats el sexo de la persona as the topic of inquiry. The second version spells out the content of the question more directly.

Both are grammatical, but the original sentence is very natural.

It is grammatical and understandable in Spain, especially in a formal, medical, legal, or administrative context.

In everyday conversation, people might choose wording depending on the situation, for example:

• Preguntaron si era hombre o mujer.
• Preguntaron por el género de la persona.
• Preguntaron cuál era su sexo.

Which version sounds most natural depends on context and on whether the speaker means biological sex, legal sex, or gender identity. The original sentence sounds fairly formal and neutral.