Who were they invented by?

英 美
  • 它们是被谁发明的?
  • invented v.发明;创造,捏造(动词invent的过去式和过去分词)adj.已发明的
  • they pron.他们
  • were v.是,在,有(be动词的复数过去式)
  • who pron.谁abbr.世界卫生组织(=WorldHealthOrganization)