阅读理解
Flags have existed for over 3000 years. The earliest flags were wooden or metal poles topped with
a carving(雕刻品). About 2000 years ago pieces of fabric were added to some poles for decoration.
Over the next 500 years the free-flying part of the flag became more important.
Every country today has its own flag. Many groups and organizations also have a flag which stands
for, or symbolizes, the aims of the group.
The UN flag depicts (描绘)a world map, centered on the north pole. The map is surrounded by an
olive(橄榄)wreath(花环)symbolizing peace and co-operation. The flag is blue and white.
1. Flags have been in existence for ____
A.500 years
B. more than 3000 years
C. about 2000 years
D. between 500 and 2000 years
2. A very old flag is likely to _____.
A. be made of fabric
B. have a map on it
C. have white shapes on it
D. be made of carved wood
3. An olive wreath is used to represent_______ .
A. peace
B. purity
C. justice
D. equality
，下表是几种原子的组成和它们的相对原子质量．通过此表可总结出如“同一原子中质子数=核外电子数”等结论，请你再总结出两条规律：
