6. With a better understanding of the human body,.

scientists and physicians will be able to cure more diseases.

5. To ensure safety, the train is controlled by an advanced

computer system.

4. They realize that it is of great value to record and teach

them to the younger generation.

3. Mobile phones stop teenagers from spending money on

clothes or cigarettes.

2. There are six spoken languages that are considered to

be native to the British Isles as well as two local accents.

1. ... to see it as it really is: a nation of different countries

held together by a common language and culture.

30．(2000江西、天津、全国文科) 设集合A={x|x∈Z且-10≤x≤-1}，

B={x|x∈Z且|x|≤5}，则A∪B中的元素个数是(　 )

　　 (A)11　 　(B)21　 (C)16 　(D)15

29．(2000广东)已知集合，那么的真子集的个数是(　 )

(A)15　　 (B)16　　 (C)3 　　(D)4

28．(2003北京春招理科)若集合，则(　 )

　　　 A． B．　 C．　 D．

27.(2003北京文、理)设集合等于 (　 )

　　　 A．　 B．　 C．　 D．