This is a great question and different people might answer it in different ways. Of the options given, I would argue that technological history (broadly defined) is the major emphasis of the book.
If we include everything from agriculture to weapons as technology, this is a book about technology. What the book does is to look at various kinds of technologies and to ask why most of these technologies were developed first and/or more completely in Europe rather than in other parts of the world. The book asks why, for example, it was Europe that developed guns and steel rather than the Americas.
Diamond's real thrust in this book is to look at the impacts of geography on the history of the world. But he does so by looking mainly at the impact of geography on technology and, thereby, on the history of the world. Therefore, of the options given, I would say this is a book about technological history.