Right answer: las estrellas
An astronomical observatory is a place chosen to observe with more precision the celestial phenomena, among which the observations to the stars (estrellas in spanish) are included.
In this sense, the Atacama Desert (Chile), is considered as the best place on Earth to observe the sky, due to its excellent climatic and geographical conditions, low humidity and low light pollution, which allow it to have more clear nights per year. It houses diverse astronomical facilities, among which are mainly optical observatories and radio observatories.
That is why scientists from various parts of the world, go to this area of Chile to observe and study the stars.
Therefore, the correct answer is b:
Científicos de todo el mundo van a los observatorios de Chile para estudiar las estrellas.