Spanish language Q&A Forum

I know ser means ‘to be’ in terms of characteristics and estar means ‘to be’ in temporary sense or in terms of location but why does this exercise use estar for ‘to be clear’ and ‘is cloudy’ but ser for ‘can be unstable’?

how can Spanish be the second most spoken language in the world? Sure, China is probably # 1 but just the population of the U.S.A. alone at more than 400 million is greater than all the native hispanohablantes. Add in Australia, South Africa, England, Scotland and a few other countries and 2nd and 3rd place must be very close.  Almost every country conducts business in English so there are a lot of English as a second language speakers. Am I missing something?

really enjoyable seeing the action described so clearly

Un ejercicio de lectura realmente útil. Vocabulario nuevo, datos interesantes sobre España leídos con claridad y con una dicción perfecta. Gran trabajo y lo he disfrutado enormemente 

Isn’t it correct to use either un altitud as well as una altitud because even though altitud is feminine, it starts with a stressed ‘a’?

¿Cuál es el porcentaje de sal?   ??

Es al menos 5 por ciento puro.  ??

Hay al menos un 5 por ciento de impurezas.  ??

Can I say "Adivino que si" or "Adivino que no"? Thanks. 

I just saw it in the forum and I think it should be added to the lesson since it is quite common. 

Question: ¡Estén atentos! means: Pay attention!

I don't see anywhere on the lesson that explains this usage. It seems like it's being used as a command/order.