So, if you mean to say "it being occupied in the sand siloxanes" (sorry, I don't have it in front of me) then the verb should be "prevents"<br /><br />If you mean to say "the ZnOs that are occupied in the sand siloxanes" then the verb should be "prevent."<br /><br />And I know the actual wording is super off from the original text. I apologize. I'm on my phone and not computer.<br /><br />If you're still not sure, then let me know.