https://blog.international-lan.com/%e8%8b%b1%e8%aa%9e%e8%aa%9e%e6%b3%95-%e4%bb%a3%e8%a9%9e-%e9%80%a3%e6%8e%a5%e4%bb%a3%e8%a9%9e-connection-pronouns-10/
英語語法 - 代詞 - 連接代詞 Connection pronouns 10