电磁起重机应用了电磁铁，它的铁心应用的是软件，而不是钢，请你根据电磁起重机的工作过程

消化性溃疡慢性穿孔最常见的部位是（）。

A.胃大弯

B.胃或十二指肠后壁

C.胃小弯

D.胃角

E.胃前壁

室外变、配电装置距液化石油气罐不应小于（）。

A.10m

B.20m

C.25m

D.35m

阅读理解

     Fish have ears. Really. They're quite small and have no opening to the outside world carrying sound

through the body. For the past seven years, Simon Thorrold, a university professor, has been examining

fish ears, small round ear bones called otoliths.

   As fish grow, so do their otoliths. Each day, their otoliths gain a ring of calcium carbonate (碳酸钙).

By looking through a microscope (显微镜) and counting (数) these rings, Thorrold can determine the

exact age of a young fish. As a fish gets older, its otoliths no longer get daily rings. Instead, they get yearly

rings, which can also be counted, giving information about the fish's age, just like the growth rings of a

tree.

Ring counting is nothing new to fish scientists. But Thorrold has turned to a new direction. They're

examining the chemical elements (元素) of each otolith ring.

     The daily ring gives us the time, but chemistry tells us about the environment in which the fish swam on

any given day. These elements tell us about the chemistry of the water that the fish was in. It also says

something about water temperature, which determines how much of these elements will gather within

each otolith ring.

   Thorrold can tell, for example, if a fish spent time in the open ocean before entering the less salty water

of coastal areas. He can basically tell where fish are spending their time at any given stage of history.

   In the case of the Atlantic croaker, a popular saltwater food fish, Thorrold and his assistant have

successfully followed the travelling of young fish from mid-ocean to the coast, a journey of many

hundreds of miles.

   This is important to managers in the fish industry, who know nearly nothing about the whereabouts (行踪) of the young fish for most food fish in the ocean. Eager to learn about his technology, fish scientists

are now lending Thorrold their ears.

1. What can we learn about fish ears from the text? 

A. They are small soft rings.            

B. They are not seen from the outside. 

C. They are openings only on food fish.  

D. They are not used to receive sound.

2. Why does the writer compare the fish to trees? 

A. Trees gain a growth ring each day. 

B. Trees also have otoliths. 

C. Their growth rings are very small. 

D. They both have growth rings.

3. Why is it important to study the chemistry of otolith rings? 

A. The elements of the otoliths can tell the history of the sea. 

B. Chemical contents (含量) of otoliths can tell how fast fish can swim. 

C. We can know more about fish and their living environment. 

D. Scientists can know exactly how old a fish is.

4. How would you understand "fish scientists are now lending their ears"?

A. They are very interested in Thorrold's research findings.

B. They want to know where they can find fish.

C. They lend their fish for chemical studies.

D. They wonder if Thorrold can find growth rings from their ears.

按行优先顺序存储下三角矩阵Ann的非零元素，则计算非零元素a_ii(1≤j≤i≤i≤n)的地址的公式为Loc(a_ij)=Loc(a₁₁)+______。

按学科分类及体系排列来查找文献属于（）检索途径。

A.著者

B.序号

C.分类

D.主题