Answer:
c. Themselves.
Step-by-step explanation:
Reflexive pronouns are those pronouns used to refer to the same noun as the subject of the verb in the sentence. They are used when the object is the same as the subject.
In the given sentence, the reflexive pronoun to use will be "themselves". This is because the subject/pronoun is "they", thus, reflecting the subject.
Therefore, the correct answer is option c.