在工程岩体范围内，结构面按贯通情况可分为（）、部分贯通结构面以及完全贯通结构面三种类

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 2000 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（电的）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 U．S____．

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小题5:A lightning between a cloud and the earth may be 13 kilometers long，and travels at

a speed of ______．

A．30 kilometres per second．

B．3000 kilometres per second

C．3 kilometres per second

D．30，000 kilometres per second

We don't plan to go to the concert, and so they don't .

A．so do they

B．they don't too

C．neither don't they

D．they don't either

3～10kV高压架空线距地面的距离不应小于( )。

A．3.0m

B．3.5m

C．4.5m

D．5.0m

OMC与上级网管之间的接口为北向接口，采用CORBA和FTP协议。（）

简述农业规模经营的内部条件。