Quiero que mi hermana subraye las palabras importantes antes de exponer conmigo.

Because Quiero que... normally requires the present subjunctive when you are expressing what you want someone else to do.

• subraya = present indicative
• subraye = present subjunctive

So:

• Quiero que mi hermana subraya... ❌
• Quiero que mi hermana subraye... ✅

This is one of the most common patterns in Spanish: verb of wanting + que + subjunctive.

Because the speaker is expressing a wish, desire, or request about another person’s action. In Spanish, that kind of idea usually takes the subjunctive.

A very common structure is:

querer + que + another subject + subjunctive

Examples:

• Quiero que vengas.
• Quiero que estudies.
• Quiero que mi hermana subraye las palabras importantes.

If the subject stays the same, Spanish usually uses an infinitive instead:

• Quiero subrayar las palabras importantes. = I want to underline the important words.

So the difference is:

• Quiero subrayar... = I want to do it.
• Quiero que mi hermana subraye... = I want my sister to do it.

The subject is explicitly stated: mi hermana.

In Quiero que mi hermana subraye..., mi hermana is the subject of subraye. She is the one who is supposed to underline the words.

That is why the sentence does not mean that I will underline them. The underlining is assigned to my sister.

Because mi hermana is the subject of the subordinate clause, not a direct object.

Compare these:

• Quiero a mi hermana. = Here a mi hermana is the direct object.
• Quiero que mi hermana subraye... = Here mi hermana is the subject of subraye.

So there is no personal a here, because Spanish does not use the personal a with subjects.

Spanish uses antes de + infinitive when the action is expressed with an infinitive.

So:

• antes de exponer = before presenting / before giving the presentation

You would use antes de que + subjunctive if you wanted a full clause with a conjugated verb:

• antes de que exponga
• antes de que expongamos

So the main contrast is:

• antes de + infinitive
• antes de que + subjunctive

Not:

• antes que exponer ❌
• antes de que expone ❌

After antes de que, Spanish normally uses the subjunctive, not the indicative.

This is a good question because the sentence is a little context-dependent.

In antes de exponer conmigo, the infinitive exponer does not state the subject explicitly. The subject is understood from context. In many situations, the most natural reading is that my sister is the one presenting with me.

So the idea is probably:

• I want my sister to underline the important words before presenting with me.

But if you want to remove ambiguity, Spanish can make the subject clearer:

• Quiero que mi hermana subraye las palabras importantes antes de que exponga conmigo.
  = before she presents with me

or

• Quiero que mi hermana subraye las palabras importantes antes de que expongamos juntos.
  = before we present together

So the original sentence is possible, but the infinitive leaves a little room for interpretation.

Because after con, Spanish uses a special pronoun form:

• conmigo = with me
• contigo = with you
• consigo = with himself/herself/yourself/themselves (formal/reflexive contexts)

So:

• conmigo ✅
• con yo ❌

This is just a special fixed form that learners have to memorise.

Not usually. In this context, exponer means to present, especially in an oral or academic setting.

In Spain, exponer is commonly used for:

• giving a presentation
• speaking in front of a class
• presenting material formally

So here it is much closer to:

• to give a presentation
• to present

It usually does not mean to expose in the everyday English sense.

Because in Spanish, adjectives often come after the noun.

So:

• las palabras importantes = the important words

This is the normal order in Spanish. Putting the adjective before the noun is much less common and often changes the tone, emphasis, or meaning.

For a straightforward descriptive meaning, noun + adjective is the usual pattern.

Yes, and that might even sound more natural in some contexts.

• palabras importantes = important words
• palabras clave = key words / keywords

If the speaker means the words that are especially useful for the presentation, palabras clave is very common. But palabras importantes is still perfectly correct.

Yes, it is natural and grammatical.

A speaker from Spain would understand it easily, especially in a school or presentation context. The only small point is that antes de exponer conmigo can be slightly ambiguous about who exactly is presenting. If the context already makes that clear, the sentence sounds fine.

If you wanted a slightly clearer version, you could say:

• Quiero que mi hermana subraye las palabras importantes antes de que exponga conmigo.
• Quiero que mi hermana subraye las palabras importantes antes de que hagamos la exposición juntas/juntos.

But the original sentence is absolutely acceptable.

Yes, but only if the context already makes it obvious who you mean.

Spanish often omits subject pronouns and even repeated subjects when they are clear from the situation. However, in this sentence, mi hermana is useful because it identifies exactly who should do the underlining.

So:

• Quiero que mi hermana subraye... = clear and explicit
• Quiero que subraye... = possible, but only if everyone already knows who she is

Because Spanish possessives like mi, tu, su, nuestro usually go directly before the noun without an article.

So:

• mi hermana = my sister
• la mi hermana ❌

This is the normal structure:

possessive + noun

Examples:

• mi libro
• tu casa
• su profesor
• mi hermana