把句子還原成陳述句就是：This research centre is the one (that ) the foreign guests visited last week.
the one做定語從句的先行詞,后面的that可以省略,因?yàn)橄刃性~在從句中作賓語,可要可不要.如果選A或B的話,句子沒有先行詞.C的話,the foreign guests visited后就沒有賓語了,where等關(guān)系副詞引導(dǎo)定語從句時(shí)后面的從句是完整的句子.
還有一個(gè)相區(qū)別的句子：Is this the research centre that/which the foreign guests visited last week 同理,我們可以吧它還原成陳述句就是：This is the research centre that/which/省略 the foreign guests visited last week.此句中有先行詞the reasearch centre,所以用關(guān)系代詞“that/which/不填”都可以的.