2 . That was written in 1946, ________ the education system has undergone great changes.

A．when

B．during which

C．since when

D．since then

4 . 他将把郊游推迟到5月1号，那时他将有空。
He will put off the picnic until May 1st, ________ he will be free.

5 . 这个慈善项目始于两年前，当时玛丽刚刚辞去工作，希望找到一个能实现自己梦想的机 会。（when)

6 . 每年十一月的第四个礼拜四是感恩节，这天纽约市有游行活动。(fall定语从句)

7 . 互联网的时代，便捷和风险共生，唯有创新，方能在虚拟空间拥有更多获得感和感全感。（unless）

8 . Since the late 1970s, _______daily smoking among high school seniors reached 30 percent, smoking rates among youth have declined. （用适当的词填空）

9 . Mr. Smith owned this oil painting until the early 1990 s, ____________he gave it to his grandson.

A．which

B．when

C．where

D．who

10 . Directions: Complete the following sentences by using non-restrictive relative clauses.
1. Most young people think fast food, ______________________________（那些专家认为是不健康的）is fashionable and tasty.
2. Americans, ______________________________(总是匆匆忙忙的), prefer hamburger stands to restaurants.
3. Mr. Smith, ______________________________(他的夫人是中国人), speaks' Chinese fluently.
4. They flew to New York, ______________________________(他们在那儿呆了三天),and then went on 'to Washington DC.
5. They will put off the party until next week, ______________________________(那时他们的父母会在家).
6. Next week, I will go to see my former classmates, ______________________________(他们中的许多人已经结婚了).
7. The volunteers, ______________________________(绝大多数是大学生)，are willing to help the old.
8. The Earth, ______________________________ (它的70%被水覆盖), is also called the water plant.
9. These two books, ______________________________(两本都不是这个国家出版的)，have attracted millions of readers.
10. The photographs, ______________________________（没有一张是好的），cost me $100.