Thanks for the question! So this question is asking us for what could be true EXCEPT. In other words, it’s looking for something that must be false based on the stimulus. Now take a look at (D), which tells us that it’ll be eventually possible to predict schizophrenia on the basis of genetic information alone. But in the stimulus, we’re told that the brains of identical twins are genetically identical. So if one twin can be schizophrenic, and the other can’t, then that means that we need to know more than genetics, since the twins have the exact same genetics (that’s what it means to be genetically identical). Thus, (D) must be false, and is the answer to this question.
Hope this helps! Feel free to ask any other questions that you might have.