甲状腺素中含有A．铁B．硒C．钙D．碘E．氯

—Have you done most of your jobs?

—Not_______ .I will do it in a minute .[ ]

A. Neither  

B. never  

C. already  

D. yet

第二次世界大战后初期，苏联社会主义建设中存在的问题中不包括：[ ]

A、高度集中的体制日益显露弊端

B、对斯大林的个人崇拜有增无减

C、社会主义民主和法制遭到破坏

D、西方资产阶级思想大量渗透

In old times,  man considered lightning to be one of the great mysteries(神秘事物)of nature.  In fact a single flash of lightning 1. 6 kilometers long has enough electricity to light one million lamps.    

The American scientist, Benjamin Franklin, was the first to suggest that lightning is in fact electricity formed between the earth and clouds high above. It happened in 1752. In the same year, he also built the first lightning rod(避雷针)to protect buildings from being struck by lightnings.    

Modern science has discovered that lightning is very strong and powerful. A lightning between a cloud and the earth may be as long as 13 kilometers, and travels at a speed of 30 million meters per second.  Scientists have the opinion that there are about 2, 000 million flashes of lightning per year. In the United States alone, it kills almost one person per day.     The safest place to be in during an electrical storm is a closed car. Outside, one should go close to low ground for cover and not stop under a tree. Also one should stay out of water and away from metal fences. Inside a house people should keep away from open doorways and windows and not touch wires or metal things.

小题1:From this passage we know lightning is_______ .

A．one of the great mysteries of nature

B．electricity high above the earth

C．a kind of light

D．the sound from the clouds小题2:In the US _______.

A．every person can see lightning every day

B．at least one person is killed by lightning every day

C．there are about 6 million flashes of lightning per year

D．about one person per day dies from lightning小题3:During a lightning storm, it would be best if you _______.

A．stand under a tree

B．go outside

C．stay in a closed car

D．stop near windows小题4:A lightning rod can _______.

A．prevent accidents caused by lightning

B．stop lightning

C．protect buildings from being washed away

D．delay the coming of lightning

就全国而言，小麦条锈菌可能的越夏地方是（）。

A.甘肃的陇南、陇东、青海东部、四川的甘孜、阿坝以及雅安的高山区

B.云贵高原和青藏高原

C.海拔较高的地方

D.西北地区

无升力迎角有什么样的特点？对称翼型和非对称翼型的无升力迎角分别是什么样的情况？