“A And B”准则表达式表示的意思是（ ）。A．文件锁定 B．文件共享 C．

Trees are useful to man in three important ways: They provide him with wood and other products; they provide him shade;. and they help to prevent droughts（早灾）and floods.

Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important．In his eagerness to make money from trees, he has cut them down in large numbers, only to find that without them he has lost the best friends he had. And besides, he is usually too careless to plant and look after new trees. So the forests slowly disappear.

This does not only mean that man will have fewer trees. The results are even more serious: for where there are trees, their roots break up soil allowing the rain to sink in and also bind（固定）the soil, thus preventing it from being washed away easily；but where there are no trees, the rain falls on hard ground and flows away, causing floods and carrying away the rich top-soil. When the top-soil is gone, nothing remains but worthless desert.

Two thousand years ago，a rich and powerful country cut down its trees to build warships, with which to gain itself an empire(帝国）．It set up the empire, but, without its trees, its soil became poor and grew weak. When the empire fell to pieces, the home country found itself faced by floods and starvation（饥荒）．

小题1:The most important service of trees to man is that___________．

A．they give them wood and other products

B．they give them shade

C．they help him prevent droughts and floods

D．they help him made money小题2:In many parts of the world, forests slowly disappear because___________．

A．many trees have been cut down by man

B．man has not paid enough attention to planting trees

C．new trees are not looked after properly

D．all the above小题3:Land becomes desert after all trees are cut down because____________．

A．roots of trees break up the soil

B．there are too many rainfalls

C．there are no larger trees to keep rain and protect the top-soil

D．strong winds bring a lot of sand小题4:The country mentioned in the passage suffered from floods and starvation  because________.

A．it set up an empire

B．the empire fell to pieces

C．it built too many warships

D．it lost its trees小题5:Which title best fits the passage?

A．Trees and Man

B．How Trees Prevent Droughts and Floods

C．How an Empire Fell

D．A Story about Trees.

胆管内压力达到下列哪项，肝脏分泌胆汁受抑制

A．1.47kPa(15cmH₂O)

B．2.94kPa(30cmH₂O)

C．4.41 kPa(45cmH₂O)

D．7.85kPa(80cmH₂O)

E．5.88kPa(60cmH₂O)

下列哪项不属于急性化脓根尖周炎的症状（）

A.持续搏动性跳痛

B.患牙明显伸长

C.咬紧牙齿时疼痛暂缓解

D.根尖区红肿、叩痛

E.相应面部反应性水肿

心尖部出现抬举性心尖搏动的是（）

A.心肌梗死

B.高血压性心脏病

C.心包积液

D.肺源性心脏病

E.二尖瓣狭窄