问题 单项选择题

若系统中存在一个等待事务集{T0,T1,T2,…,Tn},其中,T1正等待被T1锁住的数据项D1,T1正等待被T2锁住的数据项D2,…,Tn-1正等待被Tn锁住的数据项Dn,Tn正等待被T0锁住的数据项D0,则系统处于()的工作状态。

A.封锁

B.死锁

C.循环

D.并发处理

答案

参考答案:B

阅读理解

                            

(C)

Some people say we need 

to plant trees in places

where rock concerts or

conferences are held in

order to absorb the carbon

dioxide created by the

event. This picture shows

how trees can help.

Photosynthesis (光合作用)

①Photosynthesis takes place

when there is sunlight.

② Carbon dioxide in air enters

the leaves through tiny holes

called stomata ( 气孔).

③ Leaves contain chlorophyll

( 叶绿素 ) which traps the

sun's energy.

④ Plant's roots gather water

from the soil.

⑤ Leaves use chlorophyll and

sunlight to change the water

and carbon dioxide into food,

or sugar, for the plant.

⑥ Oxygen is released into the air.

63. According to the passage, which of the following plays an important part in catching the sun's energy?

A. Roots     B. Branches     C. Leaves          D. Trunks         

64. What is the best title of the diagram(图表)?

A. How trees absorb carbon dioxide?            

B. How the air can be made cleaner?

C. Trees play an important part in our daily life.    

D. How trees get food in the soil?

65. What can be inferred from the passage?

A. the food for trees is made from the water and sugar in the soil

B. photosynthesis can't take place at night    

C. photosynthesis can take place at any time

D. trees help little in improving the air conditions

66. According to the passage, where should more trees be planted?

A. near the river                    B. near the cinema

C. along the highway                D. on the mountain

问答题