Spanish language Q&A Forum

I used comenzar for start but it was corrected to empezar. What is the difference in the usage of the two verbs?

El guía is masculine? La guía would be feminine?

It is frustrating that this program isn't teaching me something before quizzing me on it, or helping me understand why it's wrong. Am I missing something, or is the program missing something? If it's me, what am I missing? 

What about "llegar a ser", a common way of saying become in some contexts?

Also, what about when become, unlike in all the examples above, is not to do with people? E.g. The weather is becoming cold. The situation became very serious. I think these can be more difficult to resolve than the ones about people.

What about reflexive verbs as ways of saying become, e.g. enfadarse (to become angry)?

The question is: “_____ los formularios el bolígrafo se quedó sin tinta.”

I chose “Mientras yo llenaba” since the translation was “While I was filling out the forms, the pen ran out of ink.”

Kwizbot says that “rellenando” is also correct, and I’m not sure why. The sentence “Rellenando los formularios el bolígrafo se quedó sin tinta” sounds as though the pen was doing the filling out—there’s no other subject expressed.