Explanation

Marble is metamorphic. Granite is igneous. Sandstone is sedimentary. The question asks for 'not a metamorphic rock'. Both Granite and Sandstone are not metamorphic. Option D says 'both A & B', which implies Marble and Granite are not metamorphic, which is false. Therefore, the question or options are flawed. However, if forced to choose the best answer among standard MCQs, usually 'Granite' is the classic igneous rock contrasted with metamorphic marble. But strictly, Sandstone is also not metamorphic. Given the options, D is factually incorrect because A (Marble) IS metamorphic. So D cannot be correct. Between B and C, both are valid answers to 'not metamorphic'. Often in such flawed questions, Granite is the intended distractor for Marble. But technically, both B and C are correct. I will flag it as needsReview due to ambiguity/flawed options.