This is tough. I don't think it's Lord ochu or Extractor. I remember those fights ending quickly. Especially the Extractor. As for the other two well. I'm pretty sure Sinspawn's head could be defeated with two spells or so. So perhaps it's Oblitzerator? Actually I think that's the one. You need to use the crane so that the fight becomes much easier (I remember it losing tons of HP when doing so, 5000+ I think). So I guess I'll go with D). Whatever happens, happens.