下列运算中，计算结果正确的是（ ） A．a2•a3=a6 B．（a2）3=a5

阅读理解。

    There are many wetlands (湿地) in China and some of them have become the world's important wetlands.

The Chinese Yellow Sea Wetlands are among them. They are in Yancheng, Jiangsu Province. They are home

for many different kinds of birds and animals. The world's largest Milu Deer Nature Reserve (自然保护区)

is in them. More than 700 milu deer live freely there. There are not many red-crowned cranes in the world,

but every winter you can see some in the Red-crowned Cranes Nature Reserve in the Yellow Sea Wetlands. 

    The temperature in the wetlands is usually neither too high nor too low. There is a lot of rain and sunshine,

too. They are really good places for wildlife (野生生物). Offering food and home for some special kinds of

animals and birds is not the only reason why we need to protect wetlands. Wetlands are important because

they also prevent flood. But some people want to change the wetlands to make more space for farms and

buildings. This means there will be less and less space for wildlife. Luckily, more and more people are

beginning to realize the important of wetlands and wildlife. Every year, on February 2nd, many activities are

held to tell people more about wetlands.

1. The Chinese Yellow Sea Wetlands are in the _____ of China. [ ]

A. east

B. south

C. west

D. north

2. Usually the weather in the wetlands is _____.[ ]

A. hot

B. pleasant

C. cold

D. dry

3. The World Wetlands Day is on _____. [ ]

A. April 22

B. June 25

C. February 2

D. March 22

4. We must protect wetlands because _____. [ ]

A. they are home for wildlife

B. they can prevent flood

C. they can offer food to the animals and birds

D. all of the above

5. The best title for the passage is _____. [ ]

A. China's Wetlands Have All Entered the World's List

B. Wetlands-Home for Wildlife and Human Beings

C. Special Animals in the Chinese Yellow Sea Wetlands

D. Wetlands-Valuable Recourses (珍贵资源) of Land on the Earth

2004年版50美元正面底纹图案采用了彩虹印刷技术，其两边为红色，中间为黄色，色彩过渡自然、渐变。

在临床试验中，产生不依从性的可能原因有：（）

A.病人迁移外出

B.病人不再愿意作为受试者

C.病人因其他原因死亡

D.社会和家庭督促和支持病人参加

E.治疗措施有副作用，使病人放弃

尿液防腐保存时，每升尿液加甲苯()

A．1～5mL

B．5～20mL

C．25～40mL

D．45～60mL

E．65～70mL

型钢混凝土框架柱全部纵向受力钢筋的配筋率不宜小于（）。

A.0.6%

B.0.7%

C.0.8%

D.0.9%