The correct answer is D
Camila y María son trabajadoras.
This is correct because...
A)trabajador
This is masculine and singular. This would be used if the sentence was asking about one male.
B) trabajadores
This is masculine and plural. This could be used if it was asking about 2 men or 1 male and 1 female.
C) trabajadora
This is feminine and singular. Although the sentence has women, this would be used if it were only asking about one female.
D) trabajadoras
This is feminine and plural. This is correct because the sentence is describing the occupation of 2 women.