下列选项中，属于临时用电的有（） A.基建工地用电 B.市政建设用电 C.抗旱打井用

如图所示，L₁、L₂及A、B两点间的电压分别为U₁、U₂和U_AB，它们之间的关系如何？若已知U_AB="6" V，U₁="3.8" V，则U₂等于多少V？

阅读理解

     Preparing for a medical emergency involving your pet is always best accomplished before the event

takes place. This series is designed to help guide you through the important decisions about first aid, as

well as how and when to transport your pet quickly and safely to a veterinary hospital or emergency

ability.

     Veterinary Partner.com has provided this complete reference book online for you to skim through,

expanding your knowledge of dog and cat first aid.However, we encourage you to buy the book to keep

in your home or car as a quick reference during an emergency.

     This book is an emergency preparedness readyreference for dogs and cats. Wise preventive

measures, intelligent use of first aid principles, coupled with recognition of abnormal symptoms and

treatment of disorders, diseases, and problems, lead to effective health care.

     A working knowledge of this information will help you get rid of some potentially dangerous

circumstances and help you prepare for emergency situations.

     It includes information on what to do and what not to do in specific emergency situations. The authors

encourage careful reading and occasional rereading. We have tried to make this book easy to

understand, avoiding technical terms as often as possible, but defining them in context when they are

necessary.

1. What's the purpose of this passage?

A. To introduce a book, a reference about first aid for dogs and cats.

B. To introduce a website.

C. To introduce a working knowledge.

D. To encourage careful reading.

2. Why are we advised to buy the book?

A. Because it's very cheap.

B. Because it contains a working knowledge of information about dogs and cats.

C. Because it contains information on specific emergency situations.

D. Because you can keep it at hand and find knowledge of dog or cat first aid in case of an emergency.

3. Which is NOT true about the book?

A. It can enlarge the readers' knowledge of dog and cat first aid.

B. It contains the knowledge of recognition of abnormal symptoms of dogs and cats.

C. Although it contains possible technical terms, it is easy to understand.

D. You can read it on VeterinaryPartner.com.

4. What does the underlined word "veterinary" mean in Paragraph 1?

A. 应急的  

B. 兽医的

C. 紧急的  

D. 资助的

WTO的基本原则中，其最大特点是（）。

A.权利与义务平衡的原则

B.公平贸易原则

C.市场开放原则

D.非歧视原则

在分光光度法中，参比溶液的作用包括（）。

A.消除吸收池壁对光的影响

B.提高准确度

C.便于计算吸光度

D.提高检测器的灵敏度

“自古书契，多编以竹简；其用缣（细绢）帛者，谓之为纸。缣贵而简重，并不便于人。伦乃造意，用树肤、麻头及敝布、渔网以为纸。”（《后汉书·蔡伦传》）下列对此理解正确的是（）

A.据材料能得出“蔡伦是纸的发明者”这一结论

B.材料说明文字记载是我们得出历史结论的首要依据

C.人们的需求是人类科技进步的原因之一

D.降低造纸成本，追求利润最大化是古代造纸术进步的原因