Learn Spanish (Latin America): El coleccionista acaba de llegar a la subasta en la que venden el jarrón raro. - The collector has just arrived at the auction in which they sell the rare vase.

When a relative pronoun comes right after a preposition like en, de, or a, you usually need an article (el, la, los, or las) before que. Since we are referring back to la subasta (the auction), we use the feminine singular la que. So, en la que means in which.

Could I use donde instead of en la que in this sentence?

Yes! Because you are talking about a physical location where something happens, you could say a la subasta donde venden... instead. However, en la que is very common in Spanish and sounds slightly more precise, which is why it is used to say in which here.

The translation says has just arrived. Why don't we use a perfect tense like ha llegado?

To say someone has just done something, Spanish uses the structure acabar de followed by an infinitive verb. Here, acaba de llegar translates specifically to has just arrived. If you used ha llegado, it would simply mean has arrived and misses the just now feeling.

Why does coleccionista use the masculine article el if the word ends in an a?