"Ellas abren estos mensajes."
Translation:They are opening these messages.
I would translate that as: They open these messages.
For some reason, duolingo has started using continuous progressive present tense meanings as an equivalent to simple present tense questions, there's not a huge amount of difference between the actual meaning, but it's causing a lot of confusion to new learners.
Simple present tense:
ellos abren - they open
Continuous progressive present tense:
estan abriendo - they are opening
As you can see, they are opening, is not the same as they open, but duolingo is treating them as the same and I don't agree with it.
The most frustrating part of Duo using first one tense then the other, is that they don't always accept the choice we make?? That's just not right.
It could easily equal the English ¨they are opening these messages¨.
The common English usage ¨they are opening these messages today (or, for the next 3 hours)¨ but it is not actually happening NOW as we speak cannot be translated by the spanish ¨estan abriendo¨.
So ¨Ellas abren estos mensajes¨ covers both the simple present tense and the part of the English continuous tense that does not fit in Spanish continuous tense.