问题 单项选择题

承诺是受要约人同意要约的意思表示,关于承诺具体理解有误的是( )。

A.承诺应当在要约确定的期限内到达要约人
B.受要约人对要约的内容作出实质性变更的为新要约
C.承诺通知到达要约人时生效
D.撤回承诺的通知应当在承诺通知到达受要约人之前

答案

参考答案:D

解析: 承诺是受要约人同意要约的意思表示。承诺应当在要约确定的期限内到达要约人。承诺通知到达要约人时生效。承诺可以撤回,撤回承诺的通知应当在承诺通知到达要约人之前或者与承诺通知同时到达要约人。受要约人超过承诺期限发出承诺的,除要约人及时通知受要约人该承诺有效的以外,为新要约。

阅读理解

阅读理解。

     The doctor pointed to some bones on his desk. "They are a man's foot bones," he said. "They

were found inside the cave, and I have been examining them. The C14 test shows that they are

about 12,000 years old."

     "What is the C14 test?" I asked. "It's a way of finding the age of some things that had been

done long ago. The 'C' means carbon and carbon is found in all living things. It is also found in

the remains of things that lived and died thousands or millions of years ago. Plants and animals

take carbon into their bodies from the air. It stays in their remains."

     "Well, there are two kinds of carbon, called carbon 12(C12) and carbon 14 (C14). Both are

taken in together, but in living things C12 is one trillion (1012) times more plentiful (大量的) than

C14. The two kinds are different in one important aspect."

     "C14 is radioactive:it gives out rays of energy at a fixed frequency (频率). As it does so, it

changes to C12  in 5,600 years. Then in the next 5,600 years, half of the remaining C14 becomes

C12 and so on. We say that C14 has a half-life (半衰期) of 5,600 years."

     "You must have found some C14 in these bones, then," I said.

     "Yes, I did. But the C12 is now four million times more plentiful. About a quarter of the C14 

 is left. That means nearly enough, that two half-lives have passed." The doctor picked up one of the

brown toe bones. "It's 12,000 years since this toe was broken. Perhaps the man was playing football

outside-with no boots on."

1. The word "remains" in paragraph two means ______.

A. things left by ancient people

B. dead bodies

C. newly-found ancient places

D. caves where ancient people lived

2. Carbon 14 is a natural element (元素) ______.

A. but it kills quickly          

B. and we all have some in us

C. found only in bones          

D. but it disappears after 5,600 years

3. It is true that only ______.

A. C14 has a half-life                    

B. old bones have a half-life

C. radioactive materials have a half-life    

D. a living thing has a half-life

选择题