It is better to say
“Elle se peigne les cheveux »
The correct conjugation is B, font.
For the infinitive verb faire, the conjugations are:
Je fais
Tu fais
Il/Elle/On fait
Nous faisons
Vous faites
Ils/Elles font
Since the subject of the verb is Ils, the correct conjugation is font.
Simplified? If so - 1/2 is the simplified fraction for 5/10.