for what purpose did the staff at a supermaket sign a letter?
两个小疑问:
1,特殊疑问句不都是以疑问代词(what、who、which、whose)、疑问副词(when、where、why、how)、疑问形容词(what/which/whose +名词)开头提问的吗?如果不止有上述提问方式,那还有哪些提问方式呢?
2,本句中“for what purpose”似乎可以替换为why? 是否同理可证若以“for what”或者“for what sth”提问时都可以替换为why?