I have been approached by a teacher with this cloze exercise. "they have taken xrays ____________ more than 1.1 million soldiers". I advised "from" but I cannot explain why it cannot be "of" since it would be "taken photos of more than....". Any suggestions?

Thanks
Lee

PS. I work as an English teacher in a small city in China and thought that Y4000 was not too bad a salary for China. I read on this site of people saving US$500 a month. What salaries are they earning, where are they situated, and what do I need to do to get that type of salary?