Spanish language Q&A Forum

I was marked wrong for answering "Nosotros LES damos juguetes a nuestros hijos" instead of just "damos" I thought that the indirect object pronoun HAD to be used. What am I missing? When should I be using it? 

Thanks.

Are the other constructios in the green box synonymous with por lo tanto/así que?

If definite articles are used on the subject of a sentence, why are they used with ríos and vegetación? Isn't the subject of the sentence acid rain? If a word that  receives  the action of the verb (contaminar) is the object , doesn't that make ríos and vegetación objects not subjects? 

I think I've reached the limit of all my understanding of grammar in both Spanish and English. I can't get this right. I'm ready to quit.

Puse solo la mitad de la harina en el bol.

I only put half the (quantity of) flour in the bowl.

Ella tiene el doble de hermanos que él.

She has twice as many siblings as he does.

Why is it de LA harina, but not de LOS hermanos? Is the definite article always skipped after doble de? There was a quiz question for "________ tiempo" meant to be filled with doble. Would it be "el doble de" or "el doble del"? 

Hola to whoever sees this:

RE: Exercise: Theatrical courtyards at: 

https://spanish.kwiziq.com/my-languages/spanish/exercises/judge/230/459630?response=61964&page=12

Last translation in the exercise: 

and their history is interesting.

Kwizbot y su historia es interesante. 

You y su historia está interesante.

I was wondering why ser is used here instead of estar.

Thank you. Nicole