The correct answer is B. Vamos a la iglesia los domingos
Step-by-step explanation:
The purpose of a caption is to explain the content of an image of illustration. In the case presented, the image shows a church or a building that is used to worship God in Christianism, you can know this because there is a cross at the top of the building. This type of building is known as "iglesia" in Spanish, also "iglesias" are common in most Spanish speaking countries as most of the population are part of Chirsitanism or any branch of it, including Catholicism. Besides this, it is common for people to go to church on Sundays or "los domingos" in Spanish.
According to this, the best caption is "Vamos a la iglesia los domingos" because this contains the word "iglesia" that refers to the place of the image and the word "domingos" that is the day people commonly go to "la iglesia" and therefore this is appropriate because it describes the image by explaining "We go to the church on Sunday" or "Vamos a la iglesia los domingos".