Milka La Mas Dura is the correct answer because she is a Dominican rapper. The question asks for the name of a Dominican rapper, and out of the given options, Milka La Mas Dura is the only one who fits that description. La Materialista is a Dominican singer, Juliana is not known as a rapper, Ke$ha is an American singer, and Shakira is a Colombian singer. Therefore, Milka La Mas Dura is the correct answer.