答案：C/E.
翻譯：這是那所上周有一些德國(guó)朋友參觀的學(xué)校嗎?
此題最好還原成陳述句來判斷答案.
1.答案A還原成：This school is where some German friends visited last week.
即where some German friends visited last week做表語從句,但是該表語從句中的謂語動(dòng)詞visited明顯缺少賓語what,而不缺少地點(diǎn)狀語where.
由此可以排除A.
2.答案B還原成：This school is one some German friends visited last week.
即用定語從句some German friends visited last week修飾主句的表語（即先行詞）one,但是one為泛指的school,而不能代指后被定語從句所修飾的特定成分this school,如果是the one才可以.
由此可以排除B.
3.答案D還原成：This school is some German friends visited last week.
很明顯,some German friends visited last week不能單獨(dú)做此句的表語從句,因?yàn)榇藦木渲械闹^語動(dòng)詞visited后面缺少一個(gè)賓語,必須選用連接代詞what來代替并引導(dǎo)該從句.
由此可以排除D.
4.答案E還原成：This is the school that some German friends visited last week.
主句為This is the school.定語從句that some German friends visited last week修飾主句的表語（即先行詞）the school.關(guān)系代詞that代替先行詞the school,在該從句中充當(dāng)謂語動(dòng)詞visited的賓語,而且可以省略that.
答案C還原成：This is the school some German friends visited last week,即是答案E中省略that的句子.
所以,該題正確答案為C/E.