The question from Spanish to English is ''Who is the boy''? and the answer would be letter choice C) El es mi mejor amigo which means ''He is my best friend'' and that's the answer because A) means you are the science teacher and that doesn't make sense because the question is asking about the boy not you so no, not B) because it says her and it means she is from cuba which is not right because the question ask who is the boy, not girl so that's why C) is correct since it correctly makes the sentence true.