Ⅰ.用适当的关系代词或关系副词填空
1．Ancient China was a place ________ states were often at war with each other.
答案：where
2．October 1,1949 was the day ________ the People's Republic of China was founded.
答案：when
3．I don't know the reason ________ she looks unhappy today.
答案：why
