Spanish language Q&A Forum

I've been learning Spanish slowly for many years now, from taking classes, learning online, and speaking with native speakers.  My interactions in Spanish have been limited to Latin Americans, primarily due to the fact that I live somewhat close to the US/Mexico border.  In my previous learning, I've been made aware of the word "vosotros" but not much beyond that.  The conjugations I had previously been taught omitted the "vosotros" form.  I have also never heard the word "vosotros" used in any conversations.

I'm curious how common it is as the lessons I am going through have the conjugations for that form, as well as examples.  I'm not sure how much focus I should place on relearning conjugations for the vosotros form given my preference to learn Latin American Spanish.

Thank you in advance for your help!

What is the difference between Prefirieron and preferisteis other than one is used in Spain. ???  Or am I missing something. 

Luna, Mar y tú ________ dormir en un hotel de lujo.Luna, Mar and you preferred to sleep in a luxury hotel.(HINT: Conjugate "preferir" in Pretérito indefinido)

For the quiz question ¿ _____ venir a la alberca? (Do you want to come to the pool?) there are 40+ possible answers in the dropdown, including some which look like nonsense. Is this an error in the system?

the article  támbien el clima, no?

In one of the examples, "las legumbres" is translated as "pulses". Shouldn't that be "legumes"?