¿Por qué ________ eso ahí?

Question

If we use hechas, doesn't that mean "Why do you do that there?" As in, "Whenever we go to my parents' house, you always sulk in the corner and refuse to talk to anyone. Why do you do that there?"I believe hechas is just as valid as echas, but it was marked incorrect. Please either accept this answer or remove this question from the quizzes.

Silvia Píriz · Accepted Answer

Hola Scott O.
I see why this might seem confusing. However, “hechas” would not work in this sentence because it changes the grammatical structure.
The intended sentence is:
¿Por qué echas eso ahí?= Why do you throw / put that there?
Here, “echas” comes from the verb echar, meaning to throw, put, or drop. The sentence is asking about the action someone is doing with eso.
If we used “hechas”, it would normally be interpreted as the past participle or adjective from hacer (“made/done”) and would need to agree with a feminine plural noun, for example:

las cosas hechas

las tareas hechas

Since “eso” is singular, hechas cannot agree with it and grammatically the sentence would not work.
So in this case the correct answer must be echas, from echar, not hechas from hacer.
Saludos
Silvia