It is son because it is the plural third person form of ser, which expresses origin.
Answer:
The right answer is, C. Protesten.
* Es bueno que ellos protesten contra la injusticia.
Explanation:
Identifying the narrator and the time that a sentence indicates is the first step that must be taken. this is very important to be able to logically conjugate the verbs, and that these have concordance with what is being expressed
1. visito
2. entró
3. hacemos
4. salí
To my knowledge, the answer is sé.
