托福TPO16的一個句子 In 1990, new rules and guidelines were adopted in the United Kingdom that has changed the whole field of Archaeology in that country。后面的that has changed the whole field of Archaeology in that country是定語從句嗎？先行詞是不是“new rules and guidelines”。定語從句和先行詞可以分得這么開嗎？

that為主語，has changed謂語為單數，比較容易排除復數先行詞的。