Which word or phrase correctly completes this sentence?
carmen y valeria chile.
sé
conocen a
conocen
sabemos

Conocen is the conjugation of the verb conocer for the third person plural in the simple present tense. In Spanish, this sentence is used to point out habitual actions or routines. So this sentence stands for the third person plural because Carmen y Valeria can be replaced by ellos. Sé and sabemos are conjugations of the verb saber and this verb is not used when going to a place. On the other hand, conocen a is used when talking about a person. Example: Ellos conocen a Laura. Finally, this sentence can be written as follows:

Carmen y Valeria conocen Chile