Task: Question Answering
Input (English): Question: In the formation of the skin they intervene: 
 Options:  <1> Only the ectoderm. <2> The ectoderm, mesoderm and cells of the neural crest. <3> The ectoderm and mesoderm. <4> The ectoderm and cells of the neural crest. <5> Only the mesoderm.
Output (English): 2