2 . Sometimes we had to work until the early hours of the morning, ________most people were still fast asleep. (用适当的词填空)

3 . ________is known to all, the earth is round.（用适当的词填空）

4 . The clever boy made a hole in the wall, ________ which he could see what was happening inside the house. (U1非限制性定语从句练习25题) (用适当的词填空)

5 . That is________stone walls are used instead of fences around New England. (用适当的词填空)

6 . He has three sons, one of ________ is an engineer. (用适当的词填空)

7 . Do you remember the day________which we first met? (用适当的词填空)

8 . Is this the museum________you once visited? (用适当的词填空)

9 . She was not in the train _________arrived just now. (用适当的词填空)

10 . At the party she spoke to Mr. Peterson, _________ father owned the company. (用适当的词填空)