关于再生障碍性贫血的发病机制正确的（） A.造血干细胞中CD8+T细胞明显减少 B.

第三部分阅读理解(共20小题；每小题2分，满分40分)

阅读下列短文，从每题所给的四个选项(A、B、C和D)中选出最佳选项，并在答题卡上将其涂黑．

A

It was close to dusk．We came to a large，bowl-shaped nest in which we saw the gray head of a very small sea turtle popping out about half an inch out of the sand．Then we heard a rustling in the bushes behind us．A flesh-eating bird came near．

Our young guide wanted us to be quiet and watch the bird moving towards the young turtle’s

head．

The bird got closer and closer to the opening and began pecking at the young turtle’s head, trying to pull it out of the sands．

The young life was in danger．We were worried about it．One of us asked the guide，“Aren’t

you going to do something?”

He put his finger to his lips and said，“This is the way nature works．”

But we didn’t agree with him and spoke with one voice asking him to do something．So he had to go and pull the young turtle out of his hole and put it on its way towards the sea．

What happened next，however，caught everyone by surprise Soon after the young turtle was set free，lots of baby turtles—having received a wrong signal that it was safe—went out of the nest and began moving towards the sea．

Our foolishness became clear．Not only had the baby turtles come out under the mistaken impression that it was safe to do so，but their mad dash was taking place too early．The still-clear

light of dusk allowed no hiding from meat—eating birds．Within a short period of time，dozens of

baby turtles had been eaten by those birds．Our young guide quickly took a baseball cap and filled it with baby turtles．Walking into the water．he set them free．Then he wildly waved his hat to frighten off those birds．

When it was over，the joyful cries of dozens of well—fed birds rifled the air．Two of the birds stood silently on the beach hoping to catch a final，struggling baby turtle．All that could be heard was the sound of the waves beating against the sands．

Heads down，we walked slowly along the beach in the dusk．

56．At first, the guide would not help the young turtle out of the nest because____．

A．he wouldn’t mind others’business

B．he thought the young turtle liked to dash into the sea

C．he wanted the young turtles to take their own course

D．he thought the young turtle should have come out earlier

57．In fact，the first baby turtle worked as_______．

A．a clever spy to attract the birds outside B．one to get information outside the nest

C．a leader to come out first                        D．a brave guard to fight against the birds

58．From the last sentence of the passage, we know that _______．

A．they were sad because the young turtles were foolish

B．they felt very tired with the still—clear light shining

C．they came to know that their rush to help did more harm than good

D．they regretted not killing the meat—eating birds

59．According to the passage，which of the following statements may be true?

A．The young turtles were doomed (注定) to be eaten by those birds．

B．All the young turtles are eaten by dozens of birds．

C．The young turtles shouldn’t come out of their nest before it was dark．

D．The young turtles gathered to frighten off the birds．

外墙面砖阴阳角方正允许偏差（）

A、5mm

B、4mm

C、3mm

D、2mm

肩部撞击症。

账户销户前要办理哪些手续？

特殊的高速带传动，速度可达多少（）

A.60~100m/s

B.10~25m/s

C.50~120m/s

D.30~50m/s