Answer: Ellos no estan felices.
Explanation: The sentence, in spanish, is:
"Ellos no __________ felices."
And the translation would be something like:
"they ___ not happy"
Reading in the comments, I saw that the options to complete this sentence are:
Están
Estoy
Estamos
Está
First, we know that in the sentence we are talking of more of one person, because of the use of "ellos" (or they)
So we could discard the options in singular; estoy and está.
Now, the options left are two different ways to write "are":
Estamos: This would be used if the person that is talking is in the group, but in the sentence, the word used is "ellos" and it is used to refer to a group of people where the one talking is not in the group.
Estan: is used if the person that is talking is not in the groups, then this would be the right option to complete the sentence.
the finished sentence is
Ellos no estan felices.